Record when a provider user accesses a clients vault (#1496)

* Record when a provider user accesses a clients vault

* Do not allow removal from provider unless owner exists

* PR Review

* Null safe event processing
* append `Async` to async methods

src/Api/Controllers/ProviderOrganizationsController.cs

@@ -91,7 +91,7 @@ namespace Bit.Api.Controllers
             }
 
             var userId = _userService.GetProperUserId(User);
-            await _providerService.RemoveOrganization(providerId, id, userId.Value);
+            await _providerService.RemoveOrganizationAsync(providerId, id, userId.Value);
         }
     }
 }