TS-1746: ApprovalStatus as a string

[martapederiva]

Link to JIRA ticket

https://hackney.atlassian.net/browse/TS-1746

Describe this PR

What is the problem we're trying to solve

We need for ApprovalStatus to be set as a string in the Housing Search world to avoid de/serialisation issues and receive it as a string (as opposed to the current integer) in the Housing Search API response

What changes have we introduced

Changed type for ApprovalStatus, deleted unnecessary enum and references to it

Checklist

• Added end-to-end (i.e. integration) tests where necessary e.g to test complete functionality of a newly added feature
• Added tests to cover all new production code
• Added comments to the README or updated relevant documentation (add link to documentation), where necessary.
• Checked all code for possible refactoring
• [ X] Code pipeline builds correctly

Follow up actions after merging PR

Update Listener and API.