FIX: PM tags route should work for usernames with a period.

config/routes.rb

@@ -922,7 +922,7 @@ Discourse::Application.routes.draw do
       get '/' => 'tags#index'
       get '/filter/list' => 'tags#index'
       get '/filter/search' => 'tags#search'
-      get '/personal_messages/:username' => 'tags#personal_messages'
+      get '/personal_messages/:username' => 'tags#personal_messages', constraints: { username: RouteFormat.username }
       post '/upload' => 'tags#upload'
       get '/unused' => 'tags#list_unused'
       delete '/unused' => 'tags#destroy_unused'

spec/requests/tags_controller_spec.rb

@@ -520,6 +520,14 @@ describe TagsController do
         tag = response.parsed_body['tags']
         expect(tag[0]["id"]).to eq('test')
       end
+
+      it 'works with usernames with a period' do
+        admin.update!(username: "test.test")
+
+        get "/tags/personal_messages/#{admin.username}.json"
+
+        expect(response.status).to eq(200)
+      end
     end
   end