Extract Members::AuthorizedDestroyService from Members::DestroyService.

app/services/members/authorized_destroy_service.rb

+module Members
+  class AuthorizedDestroyService < BaseService
+    attr_accessor :member, :user
+
+    def initialize(member, user = nil)
+      @member, @user = member, user
+    end
+
+    def execute
+      member.destroy
+
+      if member.request? && member.user != user
+        notification_service.decline_access_request(member)
+      end
+    end
+  end
+end

app/services/members/destroy_service.rb

@@ -10,12 +10,7 @@ module Members
       unless member && can?(current_user, "destroy_#{member.type.underscore}".to_sym, member)
         raise Gitlab::Access::AccessDeniedError
       end
-
-      member.destroy
-
-      if member.request? && member.user != current_user
-        notification_service.decline_access_request(member)
-      end
+      AuthorizedDestroyService.new(member, current_user).execute
     end
   end
 end