Fix oauth2-client 3 compat, drop PHP 7 support

[garak]

Fix #141

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (72be695) to head (b571b73).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##                main      #142   +/-   ##
===========================================
  Coverage     100.00%   100.00%           
  Complexity        40        40           
===========================================
  Files              3         3           
  Lines             82        82           
===========================================
  Hits              82        82           

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[Copilot]

Pull request overview

This PR updates the library to align with league/oauth2-client v3’s ResourceOwnerInterface expectations and formally drops PHP 7 support across packaging, docs, and CI.

Changes:

• Update GoogleUser::getId() signature to return mixed for oauth2-client v3 compatibility.
• Drop PHP 7 support (Composer constraint, docs, and CI matrix).
• Document the upcoming release changes in the changelog.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/Provider/GoogleUser.php	Adds : mixed return type to getId() for oauth2-client v3 interface compatibility.
composer.json	Raises minimum PHP requirement to ^8.0.
README.md	Updates supported PHP versions list and notes where PHP 7 support can be found.
CHANGELOG.md	Adds unreleased notes for oauth2-client v3 compatibility + PHP 7 removal.
.github/workflows/ci.yml	Removes PHP 7 from CI and adds newer PHP versions to the test matrix.

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[shadowhand]

Two small changes, then good to go.

[shadowhand]

Released in version 5.0.0.