Revoke and Remove Tokens on Disconnect

[n7studios]

Summary

When the user clicks the Disconnect link at WPForms > Settings > Integrations > Kit for the specific Kit connection:

• Revokes the access and refresh tokens by calling the oauth/revoke endpoint

Unlike the other Kit Plugins, WPForms provides this 'Disconnect' functionality, and therefore will always remove the connection, including its v3/v4 credentials. As such, this Plugin doesn't need to listen to the convertkit_api_revoke_tokens hook to remove credentials, as WPForms always (and already) does this for us when the user clicks Disconnect.

Adds named parameters to tests that were missing for consistency.

Testing

• testCredentialsAndResourcesAreDeletedOnDisconnect: end to end test confirming that the API Key, API Secret, 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)