v3(services): pass error handler in instead of hoping its there

[#172144638](https://www.pivotaltracker.com/story/show/172144638)

Author: Brian Butz

app/actions/mixins/service_instance_create.rb

@@ -19,13 +19,17 @@ def validate_quotas!(e)
       raise VCAP::CloudController::ServiceInstanceCreateManaged::UnprocessableCreate.new_from_details(code) unless code.nil?
     end
 
-    def validation_error!(error, name:)
+    def validation_error!(
+      error,
+      name:,
+      validation_error_handler:
+    )
       validate_quotas!(error)
 
       if error.errors.on(:name)&.include?(:unique)
-        error!("The service instance name is taken: #{name}")
+        validation_error_handler.error!("The service instance name is taken: #{name}")
       end
-      error!(error.message)
+      validation_error_handler.error!(error.message)
     end
   end
 end

app/actions/service_instance_create_managed.rb

@@ -52,15 +52,17 @@ def create(message)
 
       pollable_job
     rescue Sequel::ValidationFailed => e
-      validation_error!(e, name: message.name)
+      validation_error!(e, name: message.name, validation_error_handler: ValidationErrorHandler.new)
     end
 
     private
 
-    def error!(message)
-      raise InvalidManagedServiceInstance.new(message)
-    end
-
     attr_reader :service_event_repository
+
+    class ValidationErrorHandler
+      def error!(message)
+        raise InvalidManagedServiceInstance.new(message)
+      end
+    end
   end
 end

app/actions/service_instance_create_user_provided.rb

@@ -29,13 +29,19 @@ def create(message)
 
       instance
     rescue Sequel::ValidationFailed => e
-      validation_error!(e, name: message.name)
+      validation_error!(
+        e,
+        name: message.name,
+        validation_error_handler: ValidationErrorHandler.new
+      )
     end
 
     private
 
-    def error!(message)
-      raise InvalidUserProvidedServiceInstance.new(message)
+    class ValidationErrorHandler
+      def error!(message)
+        raise InvalidUserProvidedServiceInstance.new(message)
+      end
     end
 
     attr_reader :service_event_repository

app/actions/service_instance_update_user_provided.rb

@@ -30,15 +30,21 @@ def update(service_instance, message)
       logger.info("Finished updating user-provided service_instance #{service_instance.guid}")
       service_instance
     rescue Sequel::ValidationFailed => e
-      validation_error!(e, name: message.name)
+      validation_error!(
+        e,
+        name: message.name,
+        validation_error_handler: ValidationErrorHandler.new
+      )
     end
 
     private
 
     attr_reader :service_event_repository
 
-    def error!(message)
-      raise UnprocessableUpdate.new(message)
+    class ValidationErrorHandler
+      def error!(message)
+        raise UnprocessableUpdate.new(message)
+      end
     end
   end
 end