#1233 Decrypt attachments on tap

[sosnovsky]

This PR implements attachments decrypt on tap, so they're not decrypted on message open.

close #1233

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Tests (delete all except exactly one):

• Tests added or updated - updated user is able to view message processing errors and user is able to view encrypted email with attachment tests

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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

[tomholub]

This looks good. That made me think: there are three types of attachments:

• plain / not encrypted
• encrypted as a separate file
• encrypted with pgp/mime (a mime message with attachments, encrypted whole)

Could you double check that the third case works after this change? Please try email with subject [enigmail] encrypted+signed+file PGP/MIME on flowcrypt.compatibiltiy account.

I supose the TS core will auto-decrypt it and return back as decrypted (plain), which should work. Worth checking though.

[sosnovsky]

Here is how it works in this branch

Simulator.Screen.Recording.-.iPhone.13.-.2022-01-20.at.22.28.17.mp4

Signature can't be verified, but I get the same error on master branch, is it okay?

[sosnovsky]

The same signature error is in browser extension, so should be good

[tomholub]

Looks perfect 👍

[tomholub]

Just the tests to fix else looks great to me.