Investigate and create proposal for modifying GBFS validator architecture

[emmambd]

If you are new to the GBFS Validator, please introduce yourself (name and organization/link to GBFS). It’s helpful to know who

👋 I'm Emma Blue, a Product Manager at MobilityData who works with our tools team on our different validators, including the GBFS one.

What is the issue and why is it an issue?

Given some issues with the current validator architecture, (highlighted in issues like #136), there's a need to change the structure so we can better scale and decouple different processes.

Entur (thanks @testower!) has been open to us leveraging their current GBFS validator (https://github.com/entur/gbfs-validator-java) to make these changes.

Please describe some potential solutions you have considered (even if they aren’t related to GBFS).

The scope of this issue is to

• Review https://github.com/entur/gbfs-validator-java and consider how we can best use it
• Crosscheck rules currently in the current GBFS validator and what's in Entur's validator
• Identify the steps and areas of complexity in making this transition, including repo transition
• Discuss plan amongst the community and MobilityData team

[Timeboxed investigation/proposal for 2-3 days]

[testower]

ℹ️ I've started an "cleanup" PR on Entur's repo, going through some improvement areas around documentation and API. Feel free to comment. entur/gbfs-validator-java#81