Guide on how to setup custom message Cognito triggers

[nadetastic]

Is your feature request related to a problem? Please describe.
Currently there doesn't exist a guide that shows how to setup and send custom messages for Cognito triggers. Specifically for CustomEmailSender and CustomSMSSender

Describe the solution you'd like
A guide that walks through how to use Amplify CLI with amplify override auth to set the custom message triggers.

Describe alternatives you've considered
N/A

Additional context
From the amplify-js repo, there is an issue around this scenario where their use case is to use 3rd party providers to send messages, where the provided work around is a short explanation that would be useful as a more detailed guide.

aws-amplify/amplify-js#3099 (comment)

[wish9919]

@nadetastic Thanks for considering this request.
I was wondering if it would be possible to provide a guide for setting up and sending custom messages for Cognito triggers. Currently, there is no documentation available, and it would be extremely helpful to have step-by-step instructions for using Amplify CLI with amplify override auth.