feat: allow credentials object

[bshaffer]

Allows for a Google\Auth\CredentialsLoader instance to be passed into the constructor of Google\Client using the credentials option, which currently exists but only supports an array or string.

$client = new Google\Client([
    'credentials' => new AnonymousCredentials()
]);

This also solves #2142, which provides a way to enable self-signed JWT, but in a more general (and useful) way.

$scope = 'https://www.googleapis.com/auth/cloud-platform';
$jsonKey = json_decode(file_get_contents('./path/to/key.json'), true);
$credentials = Google\Auth\ApplicationDefaultCredentials::makeCredentials([
    'scope' => $scope,
    'jsonKey' => $jsonKey,
]);

// Enable self-signed JWT
$credentials->useJwtAccessWithScope();

$service = new Google\Service\BigQuery([
    'credentials' => $credentials
]);

[tmatsuo]

With this change, new user code can pass a CredentialLoader.

What happens if you use the new user code with an old client library? My guess is the user will get a confusing, non actionable message (I may be wrong).

[bshaffer]

What happens if you use the new user code with an old client library? My guess is the user will get a confusing, non actionable message (I may be wrong).

Unfortunately, you're correct... a user would get an error like "Cannot use object Google\Auth\Credentials\ServiceAccountCredentials as array".

I don't see this as a blocker for two reasons: 1. we have the options documented for what's accepted, and 2) in the user guide where we're using this feature (configuring Self-Signed JWTs), we explicitly state that they will need to upgrade to v2.12 of this library to use the feature.

[tmatsuo]

@bshaffer I was wondering if there's a better way for handling this change, but... maybe the benefit outweighs the negatives.

[bshaffer]

@tmatsuo we could certainly use a different option... something like credentialsLoader. That could potentially work better... the reason I went with this method is just that the term "credentials" is used to mean the CredentialsLoader object in our google/cloud library, so I was trying to stay consistent

[realtebo]

what is the last version without this issue?

[bshaffer]

@realtebo try v2.12.1