feature: negative matches

[greenpau]

I want to be able to handle inverse matching in transforms.

1. If email field exists in the data, and it does not match, the condition is satisfied and the authp/test role gets added.
   If the field does NOT exist, then it is also a match!

      transform user {
        no suffix match email @contoso.com if exists
        action add role authp/test
      }

2. The condition is NOT satisfied when any:

• email field does not exists in the data
• the value of the email field matches

      transform user {
        no suffix match email @contoso.com
        action add role authp/test
      }

Original issue: https://github.com/greenpau/caddy-authorize/issues/80