[Vertex AI] Log server error responses without -FIRDebugEnabled

[andrewheard]

Updated logging to print response payloads even when -FIRDebugEnabled is not enabled.

Example Error Response Log

If the Vertex AI API (aiplatform.googleapis.com) is not enabled:

[FirebaseVertexAI] Response payload: {
  "error": {
    "code": 403,
    "message": "Vertex AI API has not been used in project my-project-id before or it is disabled. Enable it by visiting https://console.developers.google.com/apis/api/aiplatform.googleapis.com/overview?project=my-project-id then retry. If you enabled this API recently, wait a few minutes for the action to propagate to our systems and retry.",
    "status": "PERMISSION_DENIED",
    "details": [
      {
        "@type": "type.googleapis.com/google.rpc.Help",
        "links": [
          {
            "description": "Google developers console API activation",
            "url": "https://console.developers.google.com/apis/api/aiplatform.googleapis.com/overview?project=my-project-id"
          }
        ]
      },
      {
        "@type": "type.googleapis.com/google.rpc.ErrorInfo",
        "reason": "SERVICE_DISABLED",
        "domain": "googleapis.com",
        "metadata": {
          "service": "aiplatform.googleapis.com",
          "consumer": "projects/my-project-id"
        }
      }
    ]
  }
}

Updated logging to only print the NSHTTPURLResponse if -FIRDebugEnabled is enabled.

Example NSHTTPURLResponse Log

[FirebaseVertexAI] The server responded with an error: <NSHTTPURLResponse: 0x60000030a580> { URL: https://firebaseml.googleapis.com/v2beta/projects/my-project-id/locations/us-central1/publishers/google/models/gemini-1.5-flash-preview-0514:streamGenerateContent?alt=sse } { Status Code: 403, Headers {
    "Alt-Svc" =     (
        "h3=\":443\"; ma=2592000,h3-29=\":443\"; ma=2592000"
    );
    "Content-Length" =     (
        1048
    );
    "Content-Type" =     (
        "text/event-stream"
    );
    Date =     (
        "Tue, 21 May 2024 22:28:32 GMT"
    );
    Server =     (
        ESF
    );
    Vary =     (
        Origin,
        "X-Origin",
        Referer
    );
    "x-content-type-options" =     (
        nosniff
    );
    "x-frame-options" =     (
        SAMEORIGIN
    );
    "x-xss-protection" =     (
        0
    );
} }

These were swapped because the NSHTTPURLResponse is rarely useful for understanding an error on its own, whereas the response payload contains details to fix the problem.

#no-changelog