Revoke and Remove Tokens on Disconnect

[n7studios]

Summary

When the user clicks the Disconnect button at Settings > Kit MemberMouse:

• Revokes the access and refresh tokens by calling the oauth/revoke endpoint
• Removes the v3 API Key, v4 Access Token, v4 Refresh Token and v4 Token Expires settings from the database (this Plugin never stored or used a v3 API Secret).

Testing

• testCredentialsAndResourcesAreDeletedOnDisconnect: end to end test confirming that the API Key, Access Token and Refresh Token are deleted from the Plugin.
• testCredentialsDeletedAndInvalidWhenRevoked: integration test confirming that the credentials are deleted from the Plugin and no longer work i.e. are revoked, when the API's revoke_tokens method is called.

Checklist

• I have written a test and included it in this PR
• I have run all tests and they pass
• The code passes when running the PHP CodeSniffer
• Code meets WordPress Coding Standards for PHP, HTML, CSS and JS
• Security and Sanitization requirements have been followed
• I have assigned a reviewer or two to review this PR (if you're not sure who to assign, we can do this step for you)

[ciccio-kit]

LGTM ✅