feat: add migration for enabling solution acceptance in forum threads

Author: mystique09

migrations/21_add_enable_accept_solutions.sql

@@ -0,0 +1,11 @@
+ALTER TABLE `pph_post_assist_config`
+ADD COLUMN IF NOT EXISTS `enable_accept_solutions` BOOLEAN DEFAULT FALSE;
+
+CREATE TABLE
+    IF NOT EXISTS `pph_post_assist_config_accept_solutions` (
+        `id` INT (11) NOT NULL AUTO_INCREMENT,
+        `thread_id` INT (11) NOT NULL,
+        `post_assist_config_id` INT (11) NOT NULL,
+        `user_id` INT (11) NOT NULL,
+        `created_at` DATETIME NOT NULL,
+    );