There are a number of API that are exposed via REST but not via the Transport Client. They don't necessarily have to be implemented if the goal is feature parity with the Transport Client, yet we should probably have a look at why they were not added to the Transport Client and whether it makes sense to add their support to the high-level REST Client or not. I don't think it makes sense to add support for cat API and ingest processor grok, hence I took them out already.

• cluster remote info (@J-Bean)
• get source (@timoninmaxim)
• delete alias (@hub-cap)
  - [ ] get upgrade (@timoninmaxim)
• get grok patterns (GET /_ingest/processor/grok) (@jesinity)

taken from #27205