Continuing #452 and #453:

When a bot sends a message that exceeds the current message size restriction., the service returns a 413.

Today, in the SDK, the error is just raised, with no special handling.

Doc says 403 but its actually a 413. Needs to be fixed.

Potential considerations:

• Raise a better error message (similiar to what we do with 403s)
• Help split the larger message into chunks