refactor(messages): nested messages inside of channels

[LukeBrandon]

Description of changes:

• Moved all /messages urls to /channels/:channel_id/messages and getting channel_idfrom the path
• Updated queries for messages to filter by channel_id

[FlynnOConnell]

@LukeBrandon unfortunately, you didn't run cargo sqlx prepare before this commit. We need that command to enable building in sqlx offline mode using the query! macros.

See here for more information!

[LukeBrandon]

I need to fix the routing issue that is happening with conflicting urls

[FlynnOConnell]

looks swell