Settings connector test implemented.

[kidunot89]

Fixes #1093 .

Summary Checklist

• Test added for all connector callbacks.
• callback_whitelist_options replaced with callback_allowed_options due to the whitelist_options callback being deprecated for the allowed_options filter.

[dero]

@kidunot89 This looks great! One request: can you please update callback_update_option to take parameters in a correct order?

Right now the method signature is:

public function callback_update_option( $option, $value, $old_value )

... but the update_option hook passes the $old_value first. I believe the only thing we need to do is to switch the names of the variables there.

[kidunot89]

Fixed 👍