drep: registration-certificate, update-certificate: test anchors URLs of length > 64 and <= 128

[smelc]

Changelog

- description: |
    drep: registration-certificate, update-certificate: test anchors URLs of length > 64 and <= 128
# uncomment types applicable to the change:
  type:
  # - feature        # introduces a new feature
  # - breaking       # the API has changed in a breaking way
  # - compatible     # the API has changed but is non-breaking
  # - optimisation   # measurable performance improvements
  # - improvement    # QoL changes e.g. refactoring
  # - bugfix         # fixes a defect
  - test           # fixes/modifies tests
  # - maintenance    # not directly related to the code
  # - release        # related to a new release preparation
  # - documentation  # change in code docs, haddocks...

Context

I wrote those tests to reproduce #552. We can't reproduce it anymore, but since the bug was there at some point, and I wrote the tests anyway; I though "let's merge them".

Checklist

• Commit sequence broadly makes sense and commits have useful messages
• New tests are added if needed and existing tests are updated. See Running tests for more details
• Self-reviewed the diff

[Jimbo4350]

Nice. However we should also test the failure case and we should use hedgehog generators to test the range of allowed URLs.