modules/jooby-pac4j/src/main/java/org/jooby/pac4j/Auth.java
public <C extends Credentials, U extends CommonProfile> Auth client(
      final Function<Config, Client<C, U>> provider) {
    return client("*", provider);
  }
public <C extends Credentials, U extends CommonProfile> Auth client(
      final Function<Config, Client<C, U>> provider) {
    return client("*", provider);
  }
Add an auth client, like facebook, twitter, github, etc...Please note the require dependency
must be in the classpath.

@param provider Client to add.
@param <C> Credentials.
@param <U> CommonProfile.
@return This module.