Fix for notification setting for group with dot char in name

The issue is that Rails is parsing the dot for the :format parameter, so
we add the constraint to tell rails the dot is part of the :id
parameter.

changelogs/unreleased/fix_notification_setting_group_dot.yml

+---
+title: Fix notification setting for group with dot in name
+merge_request: 38773
+author:
+type: fixed

config/routes/profile.rb

@@ -22,7 +22,7 @@ resource :profile, only: [:show, :update] do
     end
 
     resource :notifications, only: [:show, :update] do
-      resources :groups, only: :update
+      resources :groups, only: :update, constraints: { id: Gitlab::PathRegex.full_namespace_route_regex }
     end
 
     resource :password, only: [:new, :create, :edit, :update] do

spec/routing/notifications_routing_spec.rb

@@ -10,4 +10,9 @@ RSpec.describe "notifications routing" do
   it "routes to #update" do
     expect(put("/profile/notifications")).to route_to("profiles/notifications#update")
   end
+
+  it 'routes to group #update' do
+    expect(put("/profile/notifications/groups/gitlab-org")).to route_to("profiles/groups#update", id: 'gitlab-org')
+    expect(put("/profile/notifications/groups/gitlab.org")).to route_to("profiles/groups#update", id: 'gitlab.org')
+  end
 end