Support /.well-known/host-meta.json (#32206)

app/controllers/well_known/host_meta_controller.rb

@@ -7,7 +7,23 @@ module WellKnown
     def show
       @webfinger_template = "#{webfinger_url}?resource={uri}"
       expires_in 3.days, public: true
-      render content_type: 'application/xrd+xml', formats: [:xml]
+
+      respond_to do |format|
+        format.any do
+          render content_type: 'application/xrd+xml', formats: [:xml]
+        end
+
+        format.json do
+          render json: {
+            links: [
+              {
+                rel: 'lrdd',
+                template: @webfinger_template,
+              },
+            ],
+          }
+        end
+      end
     end
   end
 end