Main fix: only assign new key value where old keys are not set
and new keys have been provided.
Refactors:
- use consistent DTO model for keypairs
- delete duplicate property assignment for new orgs
* Implement endpoints to add existing organization to provider
* Run dotnet format
* Support MOE
* Run dotnet format
* Move ProviderClientsController under AC ownership
* Move ProviderClientsControllerTests under AC ownership
* Jared's feedback