Revoke and Remove Tokens on Disconnect

[n7studios]

Summary

When the user clicks the Disconnect button at WooCommerce > Settings > Integrations > Kit:

• Revokes the access and refresh tokens by calling the oauth/revoke endpoint
• Removes the v3 API Key, v3 API Secret, v4 Access Token, v4 Refresh Token and v4 Token Expires settings from the database

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)