[Gekidou] Allow multiple posts in thread and posts in channel for a specific root or channel (#5594)

* Allow multiple posts in thread and posts in channel for a specific root or channel

* Apply suggestions from code review

Co-authored-by: Miguel Alatzar <migbot@users.noreply.github.com>

Co-authored-by: Miguel Alatzar <migbot@users.noreply.github.com>

app/database/schema/server/table_schemas/posts_in_thread.ts

@@ -10,6 +10,7 @@ const {POSTS_IN_THREAD} = MM_TABLES.SERVER;
 export default tableSchema({
     name: POSTS_IN_THREAD,
     columns: [
+        {name: 'root_id', type: 'string', isIndexed: true},
         {name: 'earliest', type: 'number'},
         {name: 'latest', type: 'number'},
     ],