docs: Add redis configuration documentation and changelog

Author: Yuri Zmytrakov

CHANGELOG.md

@@ -9,6 +9,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 ### Added
 
+- Added Redis caching configuration for navigation pagination support, enabling proper `prev` and `next` links in paginated responses. [#466](https://github.com/stac-utils/stac-fastapi-elasticsearch-opensearch/pull/466)
+
 ### Changed
 
 ### Fixed

README.md

@@ -284,6 +284,29 @@ You can customize additional settings in your `.env` file:
 > [!NOTE]
 > The variables `ES_HOST`, `ES_PORT`, `ES_USE_SSL`, `ES_VERIFY_CERTS` and `ES_TIMEOUT` apply to both Elasticsearch and OpenSearch backends, so there is no need to rename the key names to `OS_` even if you're using OpenSearch.
 
+**Redis for Navigation:**
+These Redis configuration variables enable proper navigation functionality in STAC FastAPI. The Redis cache stores navigation state for paginated results, allowing the system to maintain previous page links using tokens. The configuration supports either Redis Sentinel or Redis:
+
+| Variable                     | Description                                                                          | Default                  | Required                                                                                     |
+|------------------------------|--------------------------------------------------------------------------------------|--------------------------|---------------------------------------------------------------------------------------------|
+| **Redis Sentinel**           |                                                                                      |                          |                                                                                             |
+| `REDIS_SENTINEL_HOSTS`       | Comma-separated list of Redis Sentinel hostnames/IP addresses.                       | `""`                     | Conditional (required if using Sentinel)                                                    |
+| `REDIS_SENTINEL_PORTS`       | Comma-separated list of Redis Sentinel ports (must match order).               | `"26379"`                | Conditional (required if using Sentinel)                                                    |
+| `REDIS_SENTINEL_MASTER_NAME` | Name of the Redis master node in Sentinel configuration.                             | `"master"`               | Conditional (required if using Sentinel)                                                    |
+| **Redis**                    |                                                                                      |                          |                                                                                             |
+| `REDIS_HOST`                 | Redis server hostname or IP address for Redis configuration.                    | `""`                     | Conditional (required for standalone Redis)                                                 |
+| `REDIS_PORT`                 | Redis server port for Redis configuration.                                      | `6379`                   | Conditional (required for standalone Redis)                                                 |
+| **Both**                     |                                                                                      |                          |                                                                                             |
+| `REDIS_DB`                   | Redis database number to use for caching.                                            | `0` (Sentinel) / `0` (Standalone) | Optional                                                                                    |
+| `REDIS_MAX_CONNECTIONS`      | Maximum number of connections in the Redis connection pool.                          | `10`                     | Optional                                                                                    |
+| `REDIS_RETRY_TIMEOUT`        | Enable retry on timeout for Redis operations.                                        | `true`                   | Optional                                                                                    |
+| `REDIS_DECODE_RESPONSES`     | Automatically decode Redis responses to strings.                                     | `true`                   | Optional                                                                                    |
+| `REDIS_CLIENT_NAME`          | Client name identifier for Redis connections.                                        | `"stac-fastapi-app"`     | Optional                                                                                    |
+| `REDIS_HEALTH_CHECK_INTERVAL`| Interval in seconds for Redis health checks.                                         | `30`                     | Optional                                                                                    |
+
+> [!NOTE]
+> Use either the Sentinel configuration (`REDIS_SENTINEL_HOSTS`, `REDIS_SENTINEL_PORTS`, `REDIS_SENTINEL_MASTER_NAME`) OR the Redis configuration (`REDIS_HOST`, `REDIS_PORT`), but not both.
+
 ## Datetime-Based Index Management
 
 ### Overview