added get_thread_messages and create_forum_thread endpoints

server/sql/get_forum_owners.sql

@@ -0,0 +1,3 @@
+SELECT user_id
+FROM user_forum_owners
+WHERE forum_id = ?;

server/sql/insert_thread.sql

@@ -0,0 +1,2 @@
+INSERT INTO threads (name, forum)
+VALUES (?, ?);