server: Introduce ErrorResponse and use it in error responses

[bhufmann]

What it does

When an error is created when processing a client request, return an ErrorResponse JSON object that includes

• title: short, human-readable description of the error
• detail: optional, human-readable explanation of the error

This standardizes the error response to common data structure. The field names and purpose are inspired by RFC 9457.

For 409 errors (trace or experiment) return extended ErrorResponse containing the conflicting trace or experiment respectively.

This commit also updates the swagger documentation in respect to the ErrorResponses accordingly.

Contributes to fix issue:

eclipse-cdt-cloud/trace-server-protocol#122

How to test

• Verify using one example use case and see the returned data structure
• Thorough review to make sure that no case was missed.

Follow-ups

Update TSP specification.

Review checklist

• As an author, I have thoroughly tested my changes and carefully followed the instructions in this template

[marcdumais-work]

While reviewing eclipse-cdt-cloud/trace-server-protocol#126, a couple of "409" (conflict) responses came under scrutiny. Though they are error cases, the current ErrorResponse schema is not adequate to return all pertinent information, for these more complex cases.

The conclusion:

To cover such cases, @bhufmann suggests:

add an optional detail field in the ErrorResponse, which will [contain] a free-from map and in case of 409 I'll add such [contextually useful] information [in the new field]

[bhufmann]

While reviewing eclipse-cdt-cloud/trace-server-protocol#126, a couple of "409" (conflict) responses came under scrutiny. Though they are error cases, the current ErrorResponse schema is not adequate to return all pertinent information, for these more complex cases.

The conclusion:

To cover such cases, @bhufmann suggests:

add an optional detail field in the ErrorResponse, which will [contain] a free-from map and in case of 409 I'll add such [contextually useful] information [in the new field]

Yes, I'll add an option detail field to the ErrorResponse, that can be filled accordingly.

[MatthewKhouzam]

LGTM. I am approving but I am not sure it changes everywhere.