RDISCROWD-7895 custom error messages

[n00rsy]

Issue number of the reported bug or feature request: RDISCROWD-7895

Describe your changes

• support custom error messages in abort() calls
• Many methods already assume that this works and pass strings to abort, like abort(400, "my custom message"). Now these will actually get sent to the user and will be helpful when they are working with our API.

Some usage examples:

1. https://github.com/bloomberg/pybossa/blob/main/pybossa/api/__init__.py#L795
2. https://github.com/bloomberg/pybossa/blob/main/pybossa/api/__init__.py#L733
3. https://github.com/bloomberg/pybossa/blob/main/pybossa/api/__init__.py#L772

Testing performed
Tested locally

Additional context
Add any other context about your contribution here.