Support Service Account Authentication for Vertex AI Without gcloud CLI #392

Currently, it appears that using Vertex AI requires the gcloud CLI. url
What is the recommended way to use the ADK with Vertex AI models programmatically, without relying on the CLI tool?
for example, from a remote machine running in Docker outside of GCP?

My current approach (outside of ADK) is to create a Google service account and use the following Python code:

credentials = Credentials.from_service_account_file(GOOGLE_APPLICATION_CREDENTIALS)
vertexai.init(project=project, location=location, credentials=credentials)

Is it possible to support authentication with a Google service account for Vertex AI, so that the CLI is not required?