[_] Add draft key, use mnemonic

[TamaraFinogina]

Description

Add a function for deriving a key to encrypt email drafts. Also changes input for a database key derivation function

Checklist

• Changes have been tested locally.
• Unit tests have been written or updated as necessary.
• The code adheres to the repository's coding standards.
• Relevant documentation has been added or updated.
• No new warnings or errors have been introduced.
• SonarCloud issues have been reviewed and addressed.
• QA Passed

Testing Process

Unit tests

[xabg2]

nit: the version starts from 1.2.0

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
95.5% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud