Introducing Rector

[hulkoba]

Overview

This work is conducted in accordance with "Milestone 1: Use RectorPHP for upgrading PHPUnit tests," as outlined in the Scope of Work for the Sovereign Tech Agency Resilience Program.

Note: We open this PR on master branch. Please let us know if you want to have it elsewhere.

This PR:

• adds initial rector setup
• adds custom Rector rules for these patterns
• adds documentation for Rector rules

Run rector

This requires files in the directory path in rector.php file

vendor/bin/rector process src --dry-run

Run rector test

vendor/bin/phpunit tests --filter RuleName

[terrafrost]

I'll take a look this weekend - thanks!