Fix AI Gateway GCP credentials error

AI Gateway currently fails to start up on EKS with the following error. This error is caused by missing Application Default Credentials.

Possible Solutions

• Disable Cloud Profiler

  Disable the Cloud Profiler by setting the AIGW_GOOGLE_CLOUD_PROFILER__ENABLED environment variable to false.

• Create a Cloud Profiler Service Account

  Create a GCP service account and export the credentials JSON to Vault as a "workload secret". With a small change to the Helm charts, we can mount the workload secret as a volume. Last, set the GOOGLE_APPLICATION_CREDENTIALS environment variable to point to the location of the secret.

Error Message

Traceback (most recent call last):
  File "/home/aigateway/app/venv/ai-gateway-M6hW6iiC-py3.12/bin/ai_gateway", line 6, in <module>
    sys.exit(run_app())
             ^^^^^^^^^
  File "/home/aigateway/app/ai_gateway/main.py", line 10, in run_app
    uvicorn.run(
  File "/home/aigateway/app/venv/ai-gateway-M6hW6iiC-py3.12/lib/python3.12/site-packages/uvicorn/main.py", line 580, in run
    server.run()
  File "/home/aigateway/app/venv/ai-gateway-M6hW6iiC-py3.12/lib/python3.12/site-packages/uvicorn/server.py", line 67, in run
    return asyncio.run(self.serve(sockets=sockets))
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.12/asyncio/runners.py", line 195, in run
    return runner.run(main)
           ^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.12/asyncio/runners.py", line 118, in run
    return self._loop.run_until_complete(task)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "uvloop/loop.pyx", line 1517, in uvloop.loop.Loop.run_until_complete
  File "/home/aigateway/app/venv/ai-gateway-M6hW6iiC-py3.12/lib/python3.12/site-packages/uvicorn/server.py", line 71, in serve
    await self._serve(sockets)
  File "/home/aigateway/app/venv/ai-gateway-M6hW6iiC-py3.12/lib/python3.12/site-packages/uvicorn/server.py", line 78, in _serve
    config.load()
  File "/home/aigateway/app/venv/ai-gateway-M6hW6iiC-py3.12/lib/python3.12/site-packages/uvicorn/config.py", line 442, in load
    self.loaded_app = self.loaded_app()
                      ^^^^^^^^^^^^^^^^^
  File "/home/aigateway/app/ai_gateway/app.py", line 28, in get_app
    app = create_fast_api_server(config)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/aigateway/app/ai_gateway/api/server.py", line 166, in create_fast_api_server
    setup_profiling(config.google_cloud_profiler)
  File "/home/aigateway/app/ai_gateway/profiling.py", line 16, in setup_profiling
    googlecloudprofiler.start(
  File "/home/aigateway/app/venv/ai-gateway-M6hW6iiC-py3.12/lib/python3.12/site-packages/googlecloudprofiler/__init__.py", line 125, in start
    project_id = profiler_client.setup_auth(project_id, service_account_json_file)
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/aigateway/app/venv/ai-gateway-M6hW6iiC-py3.12/lib/python3.12/site-packages/googlecloudprofiler/client.py", line 129, in setup_auth
    self._credentials, credentials_project_id = google.auth.default(
                                                ^^^^^^^^^^^^^^^^^^^^
  File "/home/aigateway/app/venv/ai-gateway-M6hW6iiC-py3.12/lib/python3.12/site-packages/google/auth/_default.py", line 685, in default
    raise exceptions.DefaultCredentialsError(_CLOUD_SDK_MISSING_CREDENTIALS)
google.auth.exceptions.DefaultCredentialsError: Your default credentials were not found. To set up Application Default Credentials, see https://cloud.google.com/docs/authentication/external/set-up-adc for more information.