feat<events.cognito>: add support for custom email sender

[BorisLeMeec]

Issue #, if available:
#370

Description of changes:
added new event struct for support of customEmailSender messages.

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[codecov-commenter]

Codecov Report

Merging #419 (1125b60) into main (80c32f1) will not change coverage.
The diff coverage is n/a.

❗ Current head 1125b60 differs from pull request most recent head 3b3640c. Consider uploading reports for the commit 3b3640c to get more accurate results

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[bmoffatt]

LGTM, do you have an AWS docs link for this feature that I can reference?

[rubengp99]

Can we cover custom SMS sender as well?

[BorisLeMeec]

Sure, I will add the same for SMS, I have few time available atm, but asap.
@bmoffatt I'll add the link from documentation

[hgpestana]

Hey, do you have any updates on this? @BorisLeMeec, do you need any help?

[bmoffatt]

The docs don't mention a returned response, I think the sender integration isn't quite the same as the Custom Message integration

Email Sender: https://docs.aws.amazon.com/cognito/latest/developerguide/user-pool-lambda-custom-email-sender.html

The custom code of your function must then process and deliver the message.

Compare with Custom Message Trigger: https://docs.aws.amazon.com/cognito/latest/developerguide/user-pool-lambda-custom-message.html#cognito-user-pools-lambda-trigger-syntax-custom-message

In the response, specify the custom text to use in messages to your users.

[kmacmcfarlane]

Is this change still happening? Running into the need for the Email/SMS event models in a project I'm working on

[moraitisk]

Hey, @BorisLeMeec, @bmoffatt is there an update regarding the support for the custom email sender event? Are there any blockers for merging this?

[MauritsBarendregt]

Bump, any updates on this one? Anyone uses a workaround?