Problem details object not returned with 4xx-responses from app

## Describe the bug
Swagger specifies that 404 / 400 responses include a problem details object.
Currently only a string is returned.

We need to land whether the response should include the problem details object or if the swagger should be updated.

## To Reproduce
Steps to reproduce the behavior:
1. Send a bad request to the app
2. See error

## Expected behavior
Swagger matches the actual response from the controllers.

## Screenshots

Start by reproducing the bad request and comparing the controller's 400/404 response with the Swagger response definition. Review the relevant controller behavior and Swagger specification; done means the implementation and documented problem-details response agree, or the specification is corrected if the string response is intentional.

Written by the indexing model from the issue text.