[feat] Add ability to compare parameter set to an EasyPost object

[nwithan8]

Description

Re: #377

Users can now define (and down the road we can add defaults) a Match function that evaluates if a parameter set object matches an EasyPost object. Some of our users have implemented their own version of this utility, to see if a prepared parameter set matches an existing object (e.g. if the address in a shipment parameter set matches the address of a given EasyPost object, they know they don't need to make a new object).

This PR:

• Add "Matches" function at base level of all parameter sets to test if a given set matches a provided EasyPostObject-based object
  • This can be implemented by library maintainers with "default" functions, or end-users can implement their own.

Testing

• Add unit tests to confirm function can be implemented and works as expected

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)

[Justintime50]

We'll want to remember to call out in the CHANGELOG that we fixed the Shipment -> Batch reference in addition to the new feature