Fixes inferring project from service account and get credentials from google.auth.default

[ahuang11]

Summary

• Previously, tried to get the project attribute from service account, but project_id is the proper attribute.
• (https://github.com/PrefectHQ/prefect-dbt/blob/main/prefect_dbt/cli/configs/base.py#L55)
• explicitly call google.auth.default to get a credentials object if no service_account* is specified

Relevant Issue(s)

I think calling google.auth.default will resolve PrefectHQ/prefect-dbt#56 so the profile.yml can be populated from a credentials object

Checklist

• Summarized PR's changes in CHANGELOG.md

[desertaxle]

Most of these changes look good, but I don't think that we should add an infer_project attribute. I included my reasoning below, so let me know what you think.

[ahuang11]

Strange that the tests are failing from:

packages/prefect/testing/standard_test_suites/__init__.py:2: in <module>
    from .blocks import BlockStandardTestSuite
/opt/hostedtoolcache/Python/3.7.14/x64/lib/python3.7/site-packages/prefect/testing/standard_test_suites/blocks.py:7: in <module>
    from PIL import Image

But Prefect has pillow pinned:
https://github.com/PrefectHQ/prefect/blob/main/requirements-dev.txt#L14

Any thoughts?

[ahuang11]

I think I may need to mock out google.auth.default()

    @pytest.fixture
    def gcp_credentials():
>       gcp_credentials_mock = GcpCredentials(project="gcp_credentials_project")

tests/conftest.py:154: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
/opt/hostedtoolcache/Python/3.7.14/x64/lib/python3.7/site-packages/prefect/blocks/core.py:176: in __init__
    self.block_initialization()
prefect_gcp/credentials.py:119: in block_initialization
    credentials = self.get_credentials_from_service_account()
prefect_gcp/credentials.py:139: in get_credentials_from_service_account
    credentials, _ = google.auth.default()

[ahuang11]

I just tried logging in through gcloud auth application-default login

It generates a file in:
~/.config/gcloud/application_default_credentials.json

Formatted as follows:

{
  "client_id": "id123",
  "client_secret": "secret123",
  "quota_project_id": "project_id",
  "refresh_token": "refresh_token",
  "type": "authorized_user"
}

So I actually need to search for both project_id and quota_project_id