Add caching for identities

[Flo4604]

Whenever we do db.Query.FindIdentityWithRatelimits we should wrap this with one of our caches.

To do this the following has to be done

• [ ] Add new cache into go/internal/services/caches/caches.go
• [ ] Use the cache in all handlers where we call this function
• [ ] Use the cache and pass it into the given handler(s) when
  • [ ] registering in the api start
  • [ ] in all tests

[linear[bot]]

ENG-2143

[Akhileshait]

Hi @Flo4604 I would like to work on this issue.