Display more errors from mailster

Hi, I improved the validate and add_subscriber function in classes/contactform.class.php to allow contact from7 to display more errors from mailster instead of just error messages for duplicate subscribers.

	public function validate( $result, $tags ) {

		if ( ! $result->is_valid() ) {
			return $result;
		}

		if ( ! function_exists( 'mailster' ) ) {
			return $result;
		}

		$submission = WPCF7_Submission::get_instance();

		if ( ! $submission || ! $posted_data = $submission->get_posted_data() ) {
			return $result;
		}

		$form = WPCF7_ContactForm::get_current();

		$properties = $form->get_properties();

		// no Mailster settings
		if ( ! isset( $properties['mailster'] ) ) {
			return $result;
		}
		$properties = $properties['mailster'];

		// not enabled
		if ( ! $properties['enabled'] ) {
			return $result;
		}

		// checkbox defined but not checked
		if ( isset( $properties['checkbox'] ) && $properties['checkbox'] && empty( $posted_data[ $properties['checkboxfield'] ][0] ) ) {
			return $result;
		}

		$this->userdata = array();
		$tag_keys       = array_flip( array_filter( wp_list_pluck( $tags, 'name' ) ) );

		foreach ( $properties['fields'] as $field => $tag ) {
			$this->userdata[ $field ] = is_array( $posted_data[ $tag ] ) ? $posted_data[ $tag ][0] : $posted_data[ $tag ];
		}

		$this->userdata['status'] = $properties['doubleoptin'] ? 0 : 1;

		if ( isset( $properties['gdpr_timestamp'] ) && $properties['gdpr_timestamp'] ) {
			$this->userdata['gdpr'] = time();
		}

		$this->userdata = apply_filters( 'mailster_verify_subscriber', $this->userdata );

		if ( is_wp_error( $this->userdata ) ) {

			$result->invalidate( $tags[ $tag_keys[ $properties['fields'][ $this->userdata->get_error_code() ] ] ], $this->userdata->get_error_message() );
			return $result;
		}

		$overwrite = $properties['overwrite'];


		

		if ( ! $overwrite && mailster( 'subscribers' )->get_by_mail( $this->userdata['email'] ) ) {
			$error_message = isset( $properties['error_message'] ) ? $properties['error_message'] : __( 'You are already registered!', 'mailster-cf7' );
			$result->invalidate( $tags[ $tag_keys[ $properties['fields']['email'] ] ], $error_message );
			return $result;
		}
		//new add+
		$add_message= $this->add_subscriber(null);
		if(!empty($add_message)) {
			$result->invalidate( $tags[ $tag_keys[ $properties['fields']['email'] ] ], $add_message );
			return $result;
	    }
//		add_action( 'wpcf7_mail_sent', array( $this, 'add_subscriber' ) );
		return $result;

	}


	/**
	 *
	 *
	 * @param unknown $contact_form
	 */
	public function add_subscriber( $contact_form ) {

		$form = WPCF7_ContactForm::get_current();

		$properties = $form->get_properties();
		$properties = $properties['mailster'];

		$list_ids  = isset( $properties['lists'] ) ? (array) $properties['lists'] : null;
		$overwrite = 1 == $properties['overwrite'];
		$merge     = 3 == $properties['overwrite'];

		// add subscriber
		$subscriber_id = mailster( 'subscribers' )->add( $this->userdata, $overwrite || $merge, $merge );

		// no error
		if ( ! is_wp_error( $subscriber_id ) && $list_ids ) {
			mailster( 'subscribers' )->assign_lists( $subscriber_id, $list_ids );
			return '';
		}else {
			return $subscriber_id->get_error_message();
		}
	}