fix(deployment): account for "null" response in parameter_openapi_schema

[mitchnielsen]

Summary

In OSS, the return value for parameter_openapi_schema is "null" instead of an empty map {}.

This leads to an inconsistent value error because the default value is the empty map "{}", but the response from the API tries to set "null".

Closes #399

Closes https://linear.app/prefect/issue/PLA-1204/resoure-prefect-deployment-error-provider-produced-inconsistent-result

Testing

We need to test against both Cloud and OSS to ensure this logic supports both cases.

For Cloud:

terraform {
  required_providers {
    prefect = {
      source = "registry.terraform.io/prefecthq/prefect"
    }
  }
}

# For a cloud instance
provider "prefect" {
  endpoint = "https://api.stg.prefect.dev"
  account_id   = "9a67b081-4f14-4035-b000-1f715f46231b"
  workspace_id = "85bad5d0-48ee-42be-9f72-8a2998512d85"
  api_key = "<redacted>"
}

resource "prefect_flow" "say_hello_flow" {
  name = "mitch-say-hello-flow"
}

resource "prefect_deployment" "hello_flow" {
  name                     = "mitch-hello-flow-deployment"
  flow_id                  = prefect_flow.say_hello_flow.id
  entrypoint               = "flows/hello_ecs_flow.py:say_hello_flow"
  version                  = "0.1"
  enforce_parameter_schema = true
  pull_steps = [
    {
      directory = "/opt/prefect"
      type      = "set_working_directory"
    },
  ]
}

You should be able to successfully apply the plan.

Next, test in OSS by modifying the compose file to match the reported version of Prefect:

diff --git a/compose.yml b/compose.yml
index b111531..b3b8fbd 100644
--- a/compose.yml
+++ b/compose.yml
@@ -4,7 +4,8 @@
 # See ./_about/CONTRIBUTING.md.
 services:
   prefect:
-    image: prefecthq/prefect:3-latest
+    image: prefecthq/prefect:3.2.9-python3.12
     ports:
       - "4200:4200"
     environment:

Then update your Terraform config to point to a local instance:

provider "prefect" {
  endpoint = "http://localhost:4200"
}

You should again be able to successfully apply the plan.

Requirements

General

• The contributing guide has been read
• Title follows the conventional commits format
• Body includes Closes <issue>, if available
• Relevant labels have been added
• Draft status is used until ready for review

Code-level changes

• Unit tests are added/updated
• Acceptance tests are added/updated (including import tests, when needed)

New or updated resource/datasource

• Documentation is added (generated by make docs from source code)
  - When applicable, provide a link back to the relevant page in the Prefect documentation site.
• For resources, the following are added:
  - Resource example under examples/resources/prefect_<name>/resource.tf
  - Import example under examples/resources/prefect_<name>/import.sh
• For datasources, the following is added:
  - Datasource example under examples/data-sources,resources>/prefect_<name>/data-source.tf