Handle exceeding the limit gracefully

[mattaschmann]

Will now return a 400 to the user with info on what the limit was that caused the error.

Overview

Currently, if a user inputs a limit that exceeds the value in the server.limits configuration variable and the value of on_exceed is error, a RunimeError will be returned. This is not ideal as it causes a 500 error to be returned to the user with no information on what caused it.

Suggested fix in this pr:

Change from a RuntimeError to a ValueError, as ValueError is already being handled to ensure that the limit is a positive number. This will also return a 400 to the user, notifying them of the limit so they can adjust their queries.

Related Issue / discussion

There is no existing issue for this. However, as it was a one line change, I consider it "trivial", and assume the discussion can happen here.

Dependency policy (RFC2)

• I have ensured that this PR meets RFC2 requirements

Updates to public demo

• I have ensured that breaking changes to the pygeoapi master demo server have been addressed
  • https://github.com/geopython/demo.pygeoapi.io/blob/master/services/pygeoapi_master/local.config.yml

Contributions and licensing

(as per https://github.com/geopython/pygeoapi/blob/master/CONTRIBUTING.md#contributions-and-licensing)

• I'd like to contribute [feature X|bugfix Y|docs|something else] to pygeoapi. I confirm that my contributions to pygeoapi will be compatible with the pygeoapi license guidelines at the time of contribution
• I have already previously agreed to the pygeoapi Contributions and Licensing Guidelines