SFR-2052: Replace OCLC Worldcat API v1 calls with v2 calls

[Apophenia]

• Creates an additional function to retrieve metadata token
• Uses that token to make calls to OCLC catalog

Discrepancies that may be related to new xml endpoint:

• "Subject" mapping sometimes contains "OCoLC" prefixes and other identifiers(?) that don't look standard
• "Is part of" field we have mapped as default doesn't seem to show up much (since we discovered it's deprecated this isn't that surprising?) but sometimes seeing a trailing semicolon in Met publications, unclear if error in data or mapping
• extra spaces before lssn in identifiers, unclear if error in data or mapping

The subject mapping is probably the most severe issue I can see when spot-checking entries.

Some of the repeated token request functionality could probably be abstracted into a utility function, but my priority was being able to run the process and check that the data looks equivalent (not yet sure it does!)