[#491] Propagate error strings from iceoryx2 via CXX API

[orecham]

Notes for Reviewer

Adds C/C++ API to retrieve pointer to string describing iceoryx2 errors.

Pre-Review Checklist for the PR Author

1. Add sensible notes for the reviewer
2. PR title is short, expressive and meaningful
3. Relevant issues are linked in the References section
4. Every source code file has a copyright header with SPDX-License-Identifier: Apache-2.0 OR MIT
5. Branch follows the naming format (iox2-123-introduce-posix-ipc-example)
6. Commits messages are according to this guideline
   • Commit messages have the issue ID ([#123] Add posix ipc example)
   • Commit author matches Eclipse Contributor Agreement (and ECA is signed)
7. Tests follow the best practice for testing
8. Changelog updated in the unreleased section including API breaking changes
9. Assign PR to reviewer
10. All checks have passed (except task-list-completed)

Checklist for the PR Reviewer

• Commits are properly organized and messages are according to the guideline
• Unit tests have been written for new behavior
• Public API is documented
• PR title describes the changes

Post-review Checklist for the PR Author

1. All open points are addressed and tracked via issues

References

Closes #491

[orecham]

This error doesn't exist in the iceoryx2 error enum.

[elfenpiff]

Good work and congratulations to the proc macro!

The only thing here is, that I would follow the iceoryx type conversion approach here and use from<EnumType, const char*> since it is a conversion from enum to a string. In this way it is nicely consistent.

[elfenpiff]

We should use here the From approach like it is done here: https://github.com/eclipse-iceoryx/iceoryx2/blob/main/iceoryx2-ffi/cxx/include/iox2/enum_translation.hpp

Since it is a conversion from enum iox2::ConfigCreationError to const char*.

This applies to all error_string() free functions.

[elfenpiff]

All those implementation should be changed to the format:

template <>
constexpr auto from<iox2::ConfigCreationError, const char *>(const iox2::ConfigCreationError value) noexcept -> const char * {
  return iox2_config_creation_error_string(iox::into<iox2_config_creation_error_e>(value));
}

[elfenpiff]

Could you also rename the file into enum_string.cpp. It makes sense to have this conversion also for non error enums like ServiceType for instance.