Replace remaining custom code for authentication with standard f!f pipes

[MLenterman]

Originally the custom code for authentication to zgw api's supported the 3 methods: jwt, basic, value. The jwt functionality has already be replaced with the JwtPipe. Basic authentication and value should also be possible to implement with standard f!f pipes. Basic is simply <username>:<password> base64 encoded I believe and in the "Authorization" header be formatted as Basic <base64 encoded token>. The value method simply allows the user to configure a static token/password that is one on one the value of the "Authorization" header.

Would recommend to move all 3 of the authorization methods to a dedicated adapter so that it can be easily reused and tested.