Custom Rules: Execute custom standard/version with custom Library Metadata

Engine has logic to detect when a standard is custom using -cs and add custom standard/version to the cache with [this pr](https://github.com/cdisc-org/cdisc-rules-engine/pull/1156). It will need a Parsing logic should be identical to a CDISC standard as maintaining the same structure would be a requirement for custom standard support. We would need to implement a CustomLibraryService as described in #1076 so as to get the metadata and parse it. This would allow full integration of custom standards/version

A/C: be able to run custom standards and version from the cache with a custom Library metadata
- will need a custom library endpoint that can be configured to get metadata which is then parsed by this class (assuming same JSON structure as CDISC library)
- associated documentation