feat(messages): added created_at field to message

[LukeBrandon]

Description of changes:

• Added the migration 0002
  • Creates a timezone-aware DateTime field on the message table that is defaulted to NOW()
  • This will automatically get set when an object is created because of the default
• Added the chrono package as well as the chrono feature for sqlx for handling these date types
• Added the created_at field to the MessageModel

Example object gotten via Fluke API:

{
    "id": 1,
    "message": "Test message",
    "created_at": "2023-06-18T23:47:56.858068Z"
}