Harden handles against invalid connector id range

[Matthias-NIDEC]

Describe your changes

If from backend site, the connectorId is not in valid range, the relevant reject is answered to avoid undefined behavior.

Issue ticket number and link

Checklist before requesting a review

• I have performed a self-review of my code
• I have made corresponding changes to the documentation
• If OCPP 2.0.1: I have updated the OCPP 2.0.1 status document
• I read the contribution documentation and made sure that my changes meet its requirements

[Pietfried]

Hi @Matthias-NIDEC , thanks for your contribution! clang-format is failing in the CI.

You can run clang-format inside the libocpp root directory using

docker run -it \
  --mount type=bind,source=$(pwd),target=/source \
  ghcr.io/everest/everest-ci/build-env-base:v1.3.3 \
  run-clang-format \
    /source \
    --extensions hpp,cpp \
    -e cache \
    --color always \
    -ri

For future PRs it would be nice if you allow maintainers to push to the branches of your fork, so do something like this without your support ;) https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/allowing-changes-to-a-pull-request-branch-created-from-a-fork