feat: add quota project to base credentials class

[busunkim96]

Make quota_project_id a property of the base credentials class and add it to the existing credentials types.

Note that I didn't make with_quota_project an abstract method on the base credentials class because that would be a breaking change.

This PR also modifies functions in default to allow a quota_project_id to be passed.

import google.auth

credentials, project = google.auth.default(quota_project_id='my-project')

import google.auth

credentials, project = google.auth.load_credentials_from_file(
    'service_account.json',
    quota_project_id='my-project'
)

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[hiranya911]

Isn't this a breaking change? Should it have been released as 1.19.0?

We are already seeing test failures in downstream libs like firebase-admin where we extend this interface.

firebase_admin/db.py:983:0: W0223: Method 'with_quota_project' is abstract in class 'Credentials' but is not overridden (abstract-method)

[hiranya911]

Actually this seems to be because pylint considers any method in an abstract class that throws NotImplementedError to be abstract: http://pylint-messages.wikidot.com/messages:w0223

Not quite sure if that should be considered a breaking change, or write it off as pylint being too pedantic.

[busunkim96]

@hiranya911

Hmm, maybe it makes more sense to have the function raise ValueError?

    def with_quota_project(self, quota_project_id):
        raise ValueError("Credentials don't support quota project.")

[mapler]

Can not find anywhere that load_credentials_from_file is called with a quota_project_id parameter.
So quota_project_id seems always be the default None.
At the same time, quota_project_id loaded in info (from json file) could have work well but overwrote by the .with_quota_project(quota_project_id)

[busunkim96]

Ah yes, it looks like I introduced a bug. Will open a PR shortly. Thanks for the review!

[hiranya911]

@busunkim96 thanks for looking into it. Yes, perhaps the default implementation in the abstract class should raise ValueError.