PHP V3 Library now updated to new OAuth2 endpoints and PKCE support

This is a PHP 8.0 and higher library that fully supports the latest Constant Contact endpoints, as it is automatically generated from the swagger.yaml file.  Changes to the swagger.yaml file are track nightly with any new updates automatically published.

You will need to turn on PHP session support for the library to authenticate.  Also make sure you update the composer version constraint as documented in the readme to make sure you get the latest releases as this library uses a date based versioning scheme.

You can find the library here https://packagist.org/packages/phpfui/constantcontact

Any problems, please open an issue on github.

Thanks