Feature/issue 732 compose pub key validation

[sosnovsky]

This PR adds pub keys validation before sending emails. It also updates encryption to use only valid keys.

close #732
close #744

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Tests (delete all except exactly one):

• Tests added or updated - added new tests for updated validation (testValidateMessageInputWithExpiredRecipientPubKey, testValidateMessageInputWithRevokedRecipientPubKey, testValidateMessageInputWithValidAndInvalidRecipientPubKeys)

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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]

@tomholub I currently have only 2 tasks assigned, can you please check which tasks should I take after these ones?

[tomholub]

Code looks good with a comment + two improvements to do in the future.

Will build and test it now

[tomholub]

I'm not too sure about this - the validation happens asynchronously as a task. Would that be of any use? By the time it figures out it's wrong, this method may already finish.

[sosnovsky]

It's just for UI, because when recipient is selected then user won't be able to see if it's highlighted with red or orange color. Evaluation result isn't used for determining valid recipients.

[tomholub]

@sosnovsky I got this crash/assertionFailure but not sure if it's related or not?

#832

[tomholub]

Otherwise works well, and that one was an assertionFailure - not too bad, so I'll merge it. The asynchronous validation can be discussed in another issue.