DEV: Add support for .well-known/apple-app-site-association (#31798)

We already support `/apple-app-site-association` at the root. Apple also
accepts `.well-known/apple-app-site-association` as a valid path so this
adds that as well, just in case.

config/routes.rb

@@ -1574,7 +1574,10 @@ Discourse::Application.routes.draw do
     get "manifest.webmanifest" => "metadata#manifest", :as => :manifest
     get "manifest.json" => "metadata#manifest"
     get ".well-known/assetlinks.json" => "metadata#app_association_android"
+    # Apple accepts either of these paths for the apple-app-site-association file
+    # Might as well support both
     get "apple-app-site-association" => "metadata#app_association_ios", :format => false
+    get ".well-known/apple-app-site-association" => "metadata#app_association_ios", :format => false
     get "opensearch" => "metadata#opensearch", :constraints => { format: :xml }
 
     scope "/tag/:tag_id" do

spec/requests/metadata_controller_spec.rb

@@ -164,6 +164,9 @@ RSpec.describe MetadataController do
     it "returns 404 by default" do
       get "/apple-app-site-association"
       expect(response.status).to eq(404)
+
+      get "/.well-known/apple-app-site-association"
+      expect(response.status).to eq(404)
     end
 
     it "returns the right output" do
@@ -181,6 +184,13 @@ RSpec.describe MetadataController do
       expect(response.media_type).to eq("application/json")
       expect(response.headers["Cache-Control"]).to eq("max-age=60, private")
 
+      get "/.well-known/apple-app-site-association"
+
+      expect(response.status).to eq(200)
+      expect(response.body).to include("applinks")
+      expect(response.media_type).to eq("application/json")
+      expect(response.headers["Cache-Control"]).to eq("max-age=60, private")
+
       get "/apple-app-site-association.json"
       expect(response.status).to eq(404)
     end