[WIP] Add extra data and defensive code for callback

[Copilot]

Thanks for the feedback on #4575. I've created this new PR, which merges into #4575, to address your comment. I will work on the changes and keep this PR's description up to date as I make progress.

Original PR: #4575
Triggering comment (#4575 (comment)):

@copilot Rework the code that posts conversationMedia to the HRM backend service. Currently requests are initiated from the flex front end plugin, or as part of the contact creation portion of the contact creation

Move all conversation media item creation to task router event handlers in the account scoped lambda. Voice recordings and transcripts media records should be created on task wrapup / completion, voicemail should continue to be executed from its current location but share common code

Retain the current flex code, have a feature flag to control whether conversationMedia items are created from Flex or the task router handler

Do this work in a separate PR