Validate login request and refactor login handling

RecNet.Domain/Profiles/Profile.cs

@@ -61,6 +61,14 @@ public class Profile
         DeviceIds.Add(deviceId);
     }
 
+    public void RecordSuccessfulLogin(string deviceId, string? platformName)
+    {
+        if (!string.IsNullOrWhiteSpace(platformName) && Name != platformName)
+            SetName(platformName);
+
+        AddDeviceId(deviceId);
+    }
+
     public void Ban()
         => IsBanned = true;