Handle error if key was not submit to Attester

[Kharchevskyi]

This PR:

• Fixes error handling if key was not submit to Attester
• Fix storing backup key in inbox

close #1304

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Tests (delete all except exactly one):

• Does not need tests (refactor only, docs or internal changes)
• Difficult to test (explain why)
• Not worth testing
• Tests will be added later (issue #...)
• 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

[Kharchevskyi]

@tomholub can you please check comments in this pr

[tomholub]

Looks ok to me overall

[tomholub]

@Kharchevskyi please check the tests later - still not passing

[sosnovsky]

All good 👍