chore(core): add function to coerce metadata

[Archento]

Proposed Changes

Metadata used in the registration should be a dict of strings. This PR coerces the data to str before sending the request.

Types of changes

• Bug fix (non-breaking change that fixes an issue).
• New feature added (non-breaking change that adds functionality).
• Breaking change (fix or feature that would cause existing functionality to stop working as expected).
• Documentation update.
• Something else (e.g., tests, scripts, example, deployment, infrastructure).

Checklist

• I have read the CONTRIBUTING guide
• Checks and tests pass locally

If applicable

• I have added tests that prove my fix is effective or that my feature works
• I have checked that code coverage does not decrease
• I have added/updated the documentation

[jrriehl]

LGTM