fix(POST /api/file): REST API endpoint returns json content-type

[iainsproat]

Description & motivation

Calls to POST /api/file/:fileType/:streamId/:branchName? returned an incorrect content-type header in its response.
The application/json content-type is now returned.

Changes:

• Content-Type header of POST /api/file/:fileType/:streamId/:branchName? endpoint is application/json
• tests assert the contents in the body of responses to POST /api/file/:fileType/:streamId/:branchName?.
• error responses to POST /api/file/:fileType/:streamId/:branchName? are valid json

To-do before merge:

Screenshots:

Validation of changes:

Checklist:

• My pull request follows the guidelines in the Contributing guide?
• My pull request does not duplicate any other open Pull Requests for the same update/change?
• My commits are related to the pull request and do not amend unrelated code or documentation.
• My code follows a similar style to existing code.
• I have added appropriate tests.
• I have updated or added relevant documentation.

References

[linear]

WEB-2065 Wrong Content Type in HTTP Response

[fabis94]

IIRC the content type is already JSON, just the headers were not set correclty, right? if so, the frontend already treats it as JSON (and it does look that way)

[iainsproat]

IIRC the content type is already JSON, just the headers were not set correclty, right? if so, the frontend already treats it as JSON (and it does look that way)

Yes, it was returning JSON in the body but the headers were not correct. Thanks for confirming the frontend behaviour @fabis94