code: public E username(String username) {
          Misc.checkNotNull(username, "username");
          this.username = username;
          //noinspection unchecked
          return (E) this;
      }
docs: Sets the username to use when authenticating with the server.
  
  Setting the username and password (using the {@link ReplicatorBuilder#password(String)})
  method
  takes precedence over credentials passed via the URI.
  
  @param username The username to use when authenticating.
  @return The current instance of {@link ReplicatorBuilder}
  @throws IllegalArgumentException if {@code username} is {@code null}.