Handle browser CORS preflight for extract-isdoc and return CORS headers from function responses

[Copilot]

Local HTML clients were failing with CORS despite portal-level * configuration because the function endpoint did not handle preflight (OPTIONS) and did not consistently emit CORS headers from application responses.

• Preflight support at function endpoint

  • Added OPTIONS to the HttpTrigger methods for extract-isdoc.
  • Short-circuits OPTIONS requests with 204 NoContent.

• Consistent CORS headers from function code

  • Added CORS headers to preflight, success, and error responses:
    • Access-Control-Allow-Origin: *
    • Access-Control-Allow-Methods: POST, OPTIONS
    • Access-Control-Allow-Headers: Content-Type, Authorization, x-functions-key

• Focused regression coverage

  • Added a unit test asserting the trigger definition includes OPTIONS, preventing accidental removal of preflight support.

[HttpTrigger(AuthorizationLevel.Function, "post", "options", Route = "extract-isdoc")]
public async Task<HttpResponseData> Run(HttpRequestData request)
{
    if (HttpMethods.IsOptions(request.Method))
    {
        var response = request.CreateResponse(HttpStatusCode.NoContent);
        AddCorsHeaders(response);
        return response;
    }

    // existing POST flow...
}

[Copilot]

Pull request overview

Adds in-function CORS handling for the extract-isdoc HTTP-triggered Azure Function so browser-based clients can successfully complete CORS preflight (OPTIONS) and receive consistent CORS headers across both success and error responses.

Changes:

• Expanded the extract-isdoc HttpTrigger to include options and short-circuit OPTIONS requests with 204 NoContent.
• Added a shared helper to attach CORS headers to preflight, success, and error responses.
• Introduced a unit test to prevent accidental removal of OPTIONS from the trigger definition.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
ExtractIsdocFunction.cs	Handles OPTIONS preflight and adds CORS headers to all responses from the function.
tests/MKTestAzureFunction.Tests/ExtractIsdocFunctionTests.cs	Adds regression test ensuring the trigger includes OPTIONS.

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