#2566 Add email signature support

[ioanmo226]

This PR added email signature support

close #2566 // if this PR closes an issue

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Tests (delete all except exactly one):

• Tests added or updated

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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

[sosnovsky]

Hi @ioanmo226, let's temporarily disable UI tests, because of their instability and quite random results.
I can check new functionality and added tests locally. After we'll fix ui tests to run consistently (or semaphore upgrades their arm64 machines) - they can be re-enabled.

[ioanmo226]

I agree but we might miss some issues if we disable UI tests.
For example, I tested deeply about current add email signature feature but missed issue where empty signature string is appended & inconsistent line breaks which was caught by UI tests. (fixed by 03945ce)

[sosnovsky]

For sure, we'll run all tests before new release, but while working on the remaining features it'll be ok to skip tests and work on failing tests (if there will be any) after fixing CI. As these failing attempts take quite long time, and in November we've already spent almost half of our previous month iOS CI budget.

[ioanmo226]

Ok, I agree

[ioanmo226]

@sosnovsky Ready for review!
Thank you