[Feature]: Support OAuth token with Vertex AI

[sean-tr]

The Feature

The documentation of litellm shows how to authenticate using JSON credentials. However, I only have access to an OAuth token. I would like to be able to do the following:

from google.oauth2.credentials import Credentials as OAuth2Credentials


temp_creds = OAuth2Credentials(credentials["token"])


cc = completion(
    model="vertex_ai/gemini-1.5-flash",
    vertex_project=credentials["project_id"],
    vertex_location=credentials["region"],
    vertex_credentials=temp_creds,
    messages=[{"role": "user", "content": "Name 3 bright colours"}],
)

To implement this myself, I think I have to modify VertexBase.load_auth to handle cases other than JSON strings and files. However, I wanted to make this issue to double-check it hasn't already been implemented and that I'm going to modify the right file.

Motivation, pitch

Motivation is explained in feature description.

Twitter / LinkedIn details

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