Add post create hook method

ee/app/models/ee/group.rb

@@ -510,5 +510,14 @@ module EE
     def invited_or_shared_group_members(groups)
       ::GroupMember.active_without_invites_and_requests.where(source_id: ::Gitlab::ObjectHierarchy.new(groups).base_and_ancestors)
     end
+
+    def execute_hooks(data, hooks_scope)
+      return unless feature_available?(:group_webhooks)
+
+      self_and_ancestor_hooks  = GroupHook.where(group_id: self.self_and_ancestors)
+      self_and_ancestor_hooks.hooks_for(hooks_scope).each do |hook|
+        hook.async_execute(data, hooks_scope.to_s)
+      end
+    end
   end
 end

ee/app/models/ee/group_member.rb

@@ -108,5 +108,10 @@ module EE
         allowed_email_domain.email_matches_domain?(email)
       end
     end
+
+    def post_create_hook
+      add_group_member_data = Gitlab::HookData::GroupMemberBuilder
+      self.source.execute_hooks(add_group_member_data, :member_hooks)
+    end
   end
 end