Improve response errors to be more descriptive

[andyslack]

When we create records via the POST endpoints we are getting a lot of generic "Bad request - please check your parameters" when incorrect information is passed.

I have noticed this in the following use cases as examples:

• When there is a unique violation, for example, trying to add a record when the record already exists.
• When we pass the wrong value type, e.g. passing a number when it should be a string.

I would like the response errors to be way more descriptive in these kinds of situations to help the developers using the API.

It would be helpful to review other use cases where better descriptions would be helpful.

We should also look at the other endpoints (update, delete, get, list) to see if there is room for improvement here.

Finally, we should write tests for these use cases with the new improved error responses to ensure full test coverage.