Add MCP probe to comprehensive health endpoint

[Copilot]

Why make this change?

• Closes [Enh]: Add MCP checks to Health Endpoint #2843
• The comprehensive /health report advertised whether MCP was enabled in its configuration block but never actually probed the MCP endpoint, so MCP outages were invisible to health monitoring.

What is this change?

• HealthCheckHelper — New UpdateMcpHealthCheckResultsAsync, wired into UpdateHealthCheckDetailsAsync alongside the data-source/entity/embeddings checks. Runs only when IsMcpEnabled; emits a HealthCheckResultEntry named mcp, tagged ["mcp"], comparing response time against the default 1000 ms threshold.
• HttpUtilities.ExecuteMcpQueryAsync — POSTs a JSON-RPC initialize request to runtimeConfig.McpPath with Accept: application/json, text/event-stream, reusing the existing CheckSanityOfUrl SSRF guard and role-header propagation. initialize is used because tools/list requires an active session under the Streamable HTTP transport.
• Utilities.CreateHttpMcpQuery — Builds the minimal initialize payload.
• HealthCheckConstants — Adds the mcp tag.

Single mcp tag (mirroring the data-source check's single data-source tag) rather than reusing endpoint, which is reserved for per-entity REST/GraphQL checks. The check is gated solely on IsMcpEnabled with a default threshold — no new config surface.

How was this tested?

• Integration Tests — extended ComprehensiveHealthEndpoint_ValidateContents to assert the mcp tag appears iff MCP is enabled.
• Unit Tests — TestHealthCheckMcpResponseAsync / TestFailureHealthCheckMcpResponseAsync cover success and non-2xx responses.

Sample Request(s)

GET /health

Resulting check entry when MCP is enabled:

{
  "name": "mcp",
  "status": "Healthy",
  "tags": ["mcp"],
  "data": { "duration-ms": 12, "threshold-ms": 1000 }
}

[Copilot]

@copilot review and address the review comments [Add MCP probe to comprehensive health endpoint by Copilot · Pull Request #3685 · Azure/data-api-builder](https://github.com/Azure/data-api-builder/pu...

Addressed in cb6fa46. I fixed the MCP review nits: added the missing semicolon in HttpUtilities, removed hardcoded MCP protocol/client version values by sourcing from McpProtocolDefaults, and tightened the MCP health-check test to assert the full initialize payload and required Accept headers.

[Copilot]

@copilot review and address the review comments [Add MCP probe to comprehensive health endpoint by Copilot · Pull Request #3685 · Azure/data-api-builder](https://github.com/Azure/data-api-builder/pu...

Addressed the latest follow-up comments in 29de25a (updated MCP health-check clientInfo.version to "1.0.0") and validated with targeted build/tests.

[souvikghosh04]

/azp run

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Azure Pipelines successfully started running 6 pipeline(s).

[souvikghosh04]

@copilot the Unit test "EmbeddingsHealthCheck_OverallStatusHealthy_WhenEmbeddingCheckIsHealthy" is failing in assertion. details- "at Azure.DataApiBuilder.Service.Tests.UnitTests.EmbeddingsHealthCheckTests.EmbeddingsHealthCheck_OverallStatusHealthy_WhenEmbeddingCheckIsHealthy() in /home/vsts/work/1/s/src/Service.Tests/UnitTests/EmbeddingsHealthCheckTests.cs:line 144
"

[Copilot]

@copilot the Unit test "EmbeddingsHealthCheck_OverallStatusHealthy_WhenEmbeddingCheckIsHealthy" is failing in assertion. details- "at Azure.DataApiBuilder.Service.Tests.UnitTests.EmbeddingsHealthCheck...

Fixed in a986526. The embeddings unit-test runtime config now disables MCP (McpRuntimeOptions(Enabled: false)) so these tests remain isolated to embeddings health behavior, and EmbeddingsHealthCheckTests passes locally.

[souvikghosh04]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 6 pipeline(s).