Add caching for "org" api calls

Add a caching for API calls to reduce the load on DB and speed frontend loading
Api calls in scope, basically all in [OrganisationController](https://github.com/testhub-io/testhub/blob/main/backend/TestsHub.Api/Controllers/OrganisationController.cs)
```
GET ​/api​/{org}
GET ​/api​/{org}​/apikey
GET ​/api​/{org}​/coverage
GET ​/api​/{org}​/testresults
```

