Implement a generic `authentication` api for web-client

Currently web-client only supports out of the box authentication for Basic and Bearer tokens. The API is designed with specific method calls for each method. We could improve this by designing a new API that would be generic and would allow future additions without breaking the API.

In web-client HttpRequest interface we should add 2 new methods:

default HttpRequest<T> authentication(AuthenticationType type, User user) {
  return authentication(type, user, null);
}

HttpRequest<T> authentication(AuthenticationType, User user, JsonObject options);

The AuthenticationType should be an enum that respects the IANA registry https://www.iana.org/assignments/http-authschemes/http-authschemes.xhtml , for example:

enum AuthenticationType {
  BASIC,
  DIGEST,
  BEARER
}

The implementation can initially use a switch statement for the enum type:

switch (type) {
  case BASIC:
    // get the username + password from `user`, concat and base64 it
    break;
  case BEARER:
    // get the access_token from `user`
    break;
  case DIGEST:
    // compute the digest using the extra options 
    break;
...

The implementation shall be trivial for BASIC and BEARER as it should do exactly what the existing code code.

Finally deprecate the old APIs and at the interface level, call the new API using default methods.

[hectorvent]

PR is done. Then I will be working on the Digest implementation.

[pmlopes]

It exists, it comes from the auth-common module. io.vertx.ext.auth.User