feat: Add carrier metadata endpoint (beta)

[nwithan8]

Description

• Add new carrier metadata endpoint (beta) to beta client
• Add custom assertion tools (.Any surprisingly missing from Xunit)

Testing

• Add unit tests, cassettes for carrier metadata

Pull Request Type

Please select the option(s) that are relevant to this PR.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Improvement (fixing a typo, updating readme, renaming a variable name, etc)

[nwithan8]

The custom assertion toolset might be a bit overzealous. I was just surprised that Xunit has a .All assertion, but not a .Any (or .Some, etc.). Rather than dealing with a boolean in a one-off unit test, I figured making a proper assertion function for it might help for reusability later on.

Just tell me to remove it like I fully anticipate happening 😄

[jchen293]

Need a changelog when releasing it later today