Modify Config Files according to health check endpoint (#2606)

## Why make this change?
Closes #2605 

## What is this change?

1. This change includes creating the new JSON format for health check
report and the related files for the same.
2. It also includes the changes required in the runtime, datasource and
entities section of the config file to support the newly updated
properties for health checks.
3. Further I have created an enhanced response writer for comprehensive
endpoint which would take up the new config changes and return the
health report and mapped it to the `/health` endpoint.

## How was this tested?

This is currently tested by making sure the basic health checks are
running as expected.
Condition 1: Health is enabled at runtime config
Here, we would get the serialized version of the basic health check.
**Note: This would be improved further.**

Condition 2: Health is disabled or null in runtime config
Here, we would get a 404 Not Found response at the page.

## Sample Request(s)
Not Found Page
<img width="821" alt="image"
src="https://github.com/user-attachments/assets/330e584c-cd96-4b61-afac-7225e5d8895d"
/>

Basic Health Check as expected
<img width="215" alt="image"
src="https://github.com/user-attachments/assets/aaa77479-28e6-4955-ae7f-72ec1ef8ff0b"
/>

Comprehensive Health Check (To Be improved further)
<img width="253" alt="image"
src="https://github.com/user-attachments/assets/cfe8e8bb-6741-4879-80a2-eee399d0654f"
/>

---------

Co-authored-by: sezalchug <[email protected]>
Co-authored-by: Aniruddh Munde <[email protected]>

Author: 3 people

src/Config/HealthCheck/ConfigurationDetails.cs

@@ -0,0 +1,17 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+namespace Azure.DataApiBuilder.Config.ObjectModel
+{
+    /// <summary>
+    /// The configuration details of the DAB Engine.
+    /// </summary>
+    public record ConfigurationDetails
+    {
+        public bool Rest { get; init; }
+        public bool GraphQL { get; init; }
+        public bool Caching { get; init; }
+        public bool Telemetry { get; init; }
+        public HostMode Mode { get; init; }
+    }
+}

src/Config/HealthCheck/DatasourceHealthCheckConfig.cs

@@ -0,0 +1,18 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+using System.Text.Json.Serialization;
+
+namespace Azure.DataApiBuilder.Config.ObjectModel;
+
+public record DatasourceHealthCheckConfig : HealthCheckConfig
+{
+    // The identifier or simple name of the data source to be checked.
+    // Required to identify data sources in case of multiple.
+    public string? Name { get; set; }
+
+    // The expected milliseconds the query took to be considered healthy.
+    // (Default: 10000ms)
+    [JsonPropertyName("threshold-ms")]
+    public int? ThresholdMs { get; set; }
+}

src/Config/HealthCheck/EntityHealthCheckConfig.cs

@@ -0,0 +1,18 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+using System.Text.Json.Serialization;
+
+namespace Azure.DataApiBuilder.Config.ObjectModel;
+
+public record EntityHealthCheckConfig : HealthCheckConfig
+{
+    // This provides the ability to specify the 'x' first rows to be returned by the query.
+    // Default is 100
+    public int? First { get; set; } = 100;
+
+    // The expected milliseconds the query took to be considered healthy.
+    // (Default: 10000ms)
+    [JsonPropertyName("threshold-ms")]
+    public int? ThresholdMs { get; set; }
+}

src/Config/HealthCheck/HealthCheckConfig.cs

@@ -0,0 +1,9 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+namespace Azure.DataApiBuilder.Config.ObjectModel;
+
+public record HealthCheckConfig
+{
+    public bool Enabled { get; set; } = true;// Default value: true
+}

src/Config/HealthCheck/RuntimeHealthCheckConfig.cs

@@ -0,0 +1,16 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+namespace Azure.DataApiBuilder.Config.ObjectModel;
+
+public record RuntimeHealthCheckConfig : HealthCheckConfig
+{
+    // TODO: Add support for caching in upcoming PRs
+    // public int cache-ttl-seconds { get; set; };
+
+    // TODO: Add support for "roles": ["anonymous", "authenticated"] in upcoming PRs
+    // public string[] Roles { get; set; };
+
+    // TODO: Add support for parallel stream to run the health check query in upcoming PRs
+    // public int MaxDop { get; set; } = 1; // Parallelized streams to run Health Check (Default: 1)
+}

src/Config/ObjectModel/DataSource.cs

@@ -12,7 +12,12 @@ namespace Azure.DataApiBuilder.Config.ObjectModel;
 /// <param name="DatabaseType">Type of database to use.</param>
 /// <param name="ConnectionString">Connection string to access the database.</param>
 /// <param name="Options">Custom options for the specific database. If there are no options, this could be null.</param>
-public record DataSource(DatabaseType DatabaseType, string ConnectionString, Dictionary<string, object?>? Options)
+/// <param name="Health">Health check configuration for the datasource.</param>
+public record DataSource(
+    DatabaseType DatabaseType,
+    string ConnectionString,
+    Dictionary<string, object?>? Options,
+    DatasourceHealthCheckConfig? Health = null)
 {
     /// <summary>
     /// Converts the <c>Options</c> dictionary into a typed options object.

src/Config/ObjectModel/Entity.cs

@@ -9,6 +9,7 @@ namespace Azure.DataApiBuilder.Config.ObjectModel;
 /// <summary>
 /// Defines the Entities that are exposed.
 /// </summary>
+/// <param name="Health">Health check configuration for the entity.</param>
 /// <param name="Source">The underlying database object to which the exposed entity is connected to.</param>
 /// <param name="Rest">The JSON may represent this as a bool or a string and we use a custom <c>JsonConverter</c> to convert that into the .NET type.</param>
 /// <param name="GraphQL">The JSON may represent this as a bool or a string and we use a custom <c>JsonConverter</c> to convert that into the .NET type.</param>
@@ -24,6 +25,7 @@ public record Entity
     public const string PROPERTY_PATH = "path";
     public const string PROPERTY_METHODS = "methods";
 
+    public EntityHealthCheckConfig? Health { get; init; }
     public EntitySource Source { get; init; }
     public EntityGraphQLOptions GraphQL { get; init; }
     public EntityRestOptions Rest { get; init; }
@@ -44,8 +46,10 @@ public Entity(
         Dictionary<string, string>? Mappings,
         Dictionary<string, EntityRelationship>? Relationships,
         EntityCacheOptions? Cache = null,
-        bool IsLinkingEntity = false)
+        bool IsLinkingEntity = false,
+        EntityHealthCheckConfig? Health = null)
     {
+        this.Health = Health;
         this.Source = Source;
         this.GraphQL = GraphQL;
         this.Rest = Rest;

src/Config/ObjectModel/HostMode.cs

@@ -1,8 +1,11 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT License.
 
+using System.Text.Json.Serialization;
+
 namespace Azure.DataApiBuilder.Config.ObjectModel;
 
+[JsonConverter(typeof(JsonStringEnumConverter))]
 public enum HostMode
 {
     Development,

src/Config/ObjectModel/RuntimeOptions.cs

@@ -8,6 +8,7 @@ namespace Azure.DataApiBuilder.Config.ObjectModel;
 
 public record RuntimeOptions
 {
+    public RuntimeHealthCheckConfig? Health { get; init; }
     public RestRuntimeOptions? Rest { get; init; }
     public GraphQLRuntimeOptions? GraphQL { get; init; }
     public HostOptions? Host { get; set; }
@@ -24,8 +25,10 @@ public RuntimeOptions(
         string? BaseRoute = null,
         TelemetryOptions? Telemetry = null,
         EntityCacheOptions? Cache = null,
-        PaginationOptions? Pagination = null)
+        PaginationOptions? Pagination = null,
+        RuntimeHealthCheckConfig? Health = null)
     {
+        this.Health = Health;
         this.Rest = Rest;
         this.GraphQL = GraphQL;
         this.Host = Host;

src/Service.Tests/Configuration/ConfigurationTests.cs

@@ -3748,7 +3748,7 @@ public async Task HealthEndpoint_ValidateContents()
             }
 
             // Validate value of 'version' property in response.
-            if (responseProperties.TryGetValue(key: DabHealthCheck.DAB_VERSION_KEY, out JsonElement versionValue))
+            if (responseProperties.TryGetValue(key: BasicHealthCheck.DAB_VERSION_KEY, out JsonElement versionValue))
             {
                 Assert.AreEqual(
                     expected: ProductInfo.GetProductVersion(),
@@ -3761,7 +3761,7 @@ public async Task HealthEndpoint_ValidateContents()
             }
 
             // Validate value of 'app-name' property in response.
-            if (responseProperties.TryGetValue(key: DabHealthCheck.DAB_APPNAME_KEY, out JsonElement appNameValue))
+            if (responseProperties.TryGetValue(key: BasicHealthCheck.DAB_APPNAME_KEY, out JsonElement appNameValue))
             {
                 Assert.AreEqual(
                     expected: ProductInfo.GetDataApiBuilderUserAgent(),