#5133 Fix broken email threading for draft messages

[martgil]

This PR fixes the broken email threading for FlowCrypt's secure draft messages.

close #5133

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Tests (delete all except exactly one):

• Does not need tests (refactor only, docs or internal changes)

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To be filled by reviewers

I have reviewed that this PR... (tick whichever items you personally focused on during this review):

• addresses the issue it closes (if any)
• code is readable and understandable
• is accompanied with tests, or tests are not needed
• is free of vulnerabilities
• is documented clearly and usefully, or doesn't need documentation

[martgil]

Hi @sosnovsky - this one is ready for review. Thank you!

Please follow the manual test below:

1. User 1 send to user 2,3 using FlowCrypt (via to, cc would work too).
2. As user 2, compose a secure reply -> go back to make a draft.
3. Access the draft from Gmail's draft folder.
4. Send the secure email reply.
5. See the sent reply as User 1, and notice you'll not be receiving replies in new thread and subject line will not prepended with term "Re:"

[sosnovsky]

Works correct now, great job on finding bug origin 👏

[martgil]

Hello @sosnovsky, I've added a few improvements, including the fix for the requested change. Thanks!

[sosnovsky]

All good now, thanks!

[martgil]

Thanks Roma for reviewing this.