Move create! method from formatters to the BaseFormatter

lib/gitlab/github_import/base_formatter.rb

@@ -9,6 +9,10 @@ module Gitlab
         @formatter = Gitlab::ImportFormatter.new
       end
 
+      def create!
+        self.klass.create!(self.attributes)
+      end
+
       private
 
       def gl_user_id(github_id)

lib/gitlab/github_import/issue_formatter.rb

@@ -16,14 +16,14 @@ module Gitlab
         }
       end
 
-      def create!
-        Issue.create!(self.attributes)
-      end
-
       def has_comments?
         raw_data.comments > 0
       end
 
+      def klass
+        Issue
+      end
+
       def number
         raw_data.number
       end

lib/gitlab/github_import/label_formatter.rb

@@ -9,8 +9,8 @@ module Gitlab
         }
       end
 
-      def create!
-        Label.create!(self.attributes)
+      def klass
+        Label
       end
 
       private

lib/gitlab/github_import/milestone_formatter.rb

@@ -14,8 +14,8 @@ module Gitlab
         }
       end
 
-      def create!
-        Milestone.create!(self.attributes)
+      def klass
+        Milestone
       end
 
       private

lib/gitlab/github_import/pull_request_formatter.rb

@@ -24,8 +24,8 @@ module Gitlab
         }
       end
 
-      def create!
-        MergeRequest.create!(self.attributes)
+      def klass
+        MergeRequest
       end
 
       def number