dev/core#2141 - composer.json - Require league/oauth2-{client,google}

[totten]

Overview

This adds two libraries for https://lab.civicrm.org/dev/core/-/issues/2141.

Split out as a separate PR to reduce risk of merge-conflicts.

[civibot]

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[eileenmcnaughton]

This has been discussed as part of the OAUTH work & these generally seem to be the leading libraries for this

[totten]

Tangentially, to clarify little something -- note that league/oauth2-client has a GenericProvider that should work with many services. I've been using it with Microsoft's OAuth2 implementation and https://github.com/bshaffer/oauth2-demo-php.

There is at least one incompatibility between GenericProvider and Google's services. (I've only seen/investigated the one incompatibility. That specific one seems more the fault of GenericProvider IMHO, but fixing it upstream would likely require a BC-break.) So that's why I pulled in their supplemental package for Google.