[Enh]: The `info.description` field in the OpenAPI output is never populated.

Summary

The info.description field in the generated OpenAPI document is never populated.

DAB already supports a server-level description through runtime.mcp.description. Use this value to populate OpenApiInfo.Description when building the OpenAPI document.

Desired behavior

When runtime.mcp.description is configured, pass its value to OpenApiInfo.Description in BuildOpenApiDocument.

Single configuration

{
  "runtime": {
    "mcp": {
      "description": "This server provides access to the company database."
    }
  }
}

Expected OpenAPI output

{
  "info": {
    "title": "Data API builder - REST Endpoint",
    "version": "1.0.0",
    "description": "This server provides access to the company database."
  }
}

Multiple configurations

When DAB uses multiple configuration files, use runtime.mcp.description from the top-level configuration.

The combined runtime produces one OpenAPI document, so it should also have one description. Runtime settings from child configuration files should not contribute separate descriptions.

Top-level configuration

{
  "data-source-files": [
    "sales.json",
    "inventory.json"
  ],
  "runtime": {
    "mcp": {
      "description": "This server provides access to company sales and inventory data."
    }
  }
}

Expected OpenAPI output

{
  "info": {
    "title": "Data API builder - REST Endpoint",
    "version": "1.0.0",
    "description": "This server provides access to company sales and inventory data."
  }
}

Current behavior

runtime.mcp.description is available in the DAB configuration and is used as the MCP server description, but OpenApiInfo.Description is never set.

As a result, the description is available to MCP clients but omitted from the generated OpenAPI document.

Recommendation

Set OpenApiInfo.Description to the resolved top-level runtime.mcp.description value in BuildOpenApiDocument.

Do not introduce a separate runtime.rest.openapi-description property. Using the existing MCP description avoids duplicate configuration and provides one consistent description for the server across MCP and OpenAPI.

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