Run delete operation in a transaction (#1055)

* Run delete operations in a transaction

* Add `after_commit` callback to delete operations

spec/avram/operations/delete_operation_callbacks_spec.cr

@@ -22,13 +22,19 @@ private class DeleteOperationWithCallbacks < User::DeleteOperation
     mark_callback("after_delete_in_a_block with #{deleted_user.name}")
   end
 
+  after_commit :run_after_commit
+
   private def update_number
     mark_callback("before_delete_update_number")
   end
 
   private def notify_complete(deleted_user)
     mark_callback("after_delete_notify_complete is #{deleted_user.name}")
   end
+
+  private def run_after_commit(deleted_user)
+    mark_callback("after_commit_#{deleted_user.name.underscore}")
+  end
 end
 
 describe "Avram::DeleteOperation callbacks" do
@@ -41,6 +47,7 @@ describe "Avram::DeleteOperation callbacks" do
       operation.callbacks_that_ran.should contain "before_delete_in_a_block"
       operation.callbacks_that_ran.should contain "after_delete_notify_complete is Jerry"
       operation.callbacks_that_ran.should contain "after_delete_in_a_block with Jerry"
+      operation.callbacks_that_ran.should contain "after_commit_jerry"
     end
   end
 end

src/avram/delete_operation.cr

@@ -35,18 +35,32 @@ abstract class Avram::DeleteOperation(T)
     T.name.underscore
   end
 
+  delegate :database, :table_name, :primary_key_name, to: T
+
   def delete : Bool
     before_delete
 
     if valid?
-      result = delete_or_soft_delete(@record)
-      @record = result
-      after_delete(@record)
-      publish_delete_success_event
-      mark_as_deleted
+      transaction_committed = database.transaction do
+        @record = delete_or_soft_delete(record)
+        after_delete(record)
+        true
+      end
+
+      if transaction_committed
+        mark_as_deleted
+        after_commit(record)
+        publish_delete_success_event
+        true
+      else
+        mark_as_failed
+        publish_delete_failed_event
+        false
+      end
     else
-      publish_delete_failed_event
       mark_as_failed
+      publish_delete_failed_event
+      false
     end
   end
 
@@ -88,6 +102,8 @@ abstract class Avram::DeleteOperation(T)
 
   def after_delete(_record : T); end
 
+  def after_commit(_record : T); end
+
   # :nodoc:
   def publish_delete_failed_event
     Avram::Events::DeleteFailedEvent.publish(