feat(message): added `updated_at` field to messages

[LukeBrandon]

Description of changes

• Added updated_at field for message table (up and down migration)
• Updated db::message::update_message to put now() into the updated_at field
• Ran cargo sqlx prepare

Testing Strategy:

• Results after running an update on a message
• Note: updated_at time was updated

  
  fluke=# select * from message;
  id |    message    |          created_at           | user_id | channel_id |          updated_at
  ----+---------------+-------------------------------+---------+------------+-------------------------------
  3 | test messaage | 2023-08-14 18:47:21.342491-05 |       1 |          3 | 2023-08-14 18:47:21.342491-05
  (1 row)

fluke=# select * from message; id | message | created_at | user_id | channel_id | updated_at ----+-----------------+-------------------------------+---------+------------+------------------------------- 3 | update messaage | 2023-08-14 18:47:21.342491-05 | 1 | 3 | 2023-08-14 18:48:06.567496-05 (1 row)