Clients should allow the quota project (user project?) to be set through client options.

The credential provided here should override any quota project attached to the credentials.

Depends on:

• feat: allow quota project to be passed to create_channel python-api-core#58
• feat: add quota project to base credentials class google-auth-library-python#546

from google.cloud import texttospeech

client = texttospeech.textToSpeechClient(
    client_options={"quota_project": "myproject-123"}
)

# requests set `X-Goog-User-Project` header to 'myproject-123'

Internal link: go/extensible-client-options-exit