fix: add comment explaining rescue Sequel::ValidationFailed in service broker registration

The around_save hook on the ServiceBroker model catches unique constraint
violations and adds errors to the model before raising ValidationFailed.
The rescue block returns nil, and callers access errors via the delegated
errors method.

Author: serdarozerr

lib/services/service_brokers/service_broker_registration.rb

@@ -31,6 +31,7 @@ def create
       end
       self
     rescue Sequel::ValidationFailed
+      # Errors have been added to the broker model by around_save (e.g. unique constraint violations)
       nil
     end
 
@@ -53,6 +54,7 @@ def update
       end
       self
     rescue Sequel::ValidationFailed
+      # Errors have been added to the broker model by around_save (e.g. unique constraint violations)
       nil
     end