Manage Pledge: Enable pledge admins to edit contributors from manage form (#108)

* Add contributor management to manage form
* Check `pledge_id` to prevent returning all contributors
* Return a plain text error string – this is used in an alert box, so it can't contain HTML
* Hide confirmation when pledge is a draft
* Only enqueue script if the user is authorized

plugins/wporg-5ftf/views/form-pledge-manage.php

@@ -33,6 +33,11 @@ require __DIR__ . '/partial-result-messages.php';
 				value="<?php esc_attr_e( 'Update Pledge', 'wporg-5ftf' ); ?>"
 			/>
 		</div>
+
+		<h2><?php esc_html_e( 'Contributors', 'wporg-5ftf' ); ?></h2>
+
+		<?php require get_views_path() . 'manage-contributors.php'; ?>
+
 	</form>
 
 <?php endif; ?>