Added existed user logic

[mazhutoanton]

The goal of the pull request is not only to propose a working code as a solution to the requirement.
It is a tool for you to give context and explanation of your approach to the problem,
and transfer the knowledge to your team members.

Checklist (Mandatory):

• I have a JIRA issue for this PR (link)
• I have added a record to the CHANGELOG.md
• I have tested new code locally
• I have done a smoke test of the larger feature locally
• I have merged the master (parent) branch into my feature branch and resolved all conflicts
• I have added tests that prove my fix/implementation is effective or that my feature works

Checklist (Optional):

• I have written the code according to the adopted style guide?

Additional notes

• ...