code: @NonNull
      public EmailIntentBuilder to(@NonNull Collection<String> to) {
          checkNotNull(to);
          for (String email : to) {
              checkEmail(email);
          }
          this.to.addAll(to);
  
          return this;
      }
docs: Add a list of email addresses to be used in the "to" field.
  
  @param to
  the email addresses to add
  
  @return This {@code EmailIntentBuilder} for method chaining