Add endpoints for getting webpush public key and subscribing

app/controllers/ajax/web_push_controller.rb

@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+class Ajax::WebPushController < AjaxController
+  def key
+    certificate = Rpush::Webpush::App.find_by(name: "webpush").certificate
+
+    @response[:key] = JSON.parse(certificate)["public_key"]
+  end
+
+  def subscribe
+    WebPushSubscription.create!(
+      user:         current_user,
+      subscription: params[:subscription]
+    )
+
+    @response[:status] = :okay
+    @response[:success] = true
+  end
+end

config/routes.rb

@@ -132,6 +132,8 @@ Rails.application.routes.draw do
     post "/list_membership", to: "list#membership", as: :list_membership
     post "/subscribe", to: "subscription#subscribe", as: :subscribe_answer
     post "/unsubscribe", to: "subscription#unsubscribe", as: :unsubscribe_answer
+    get "/webpush/key", to: "web_push#key", as: :webpush_key
+    post "/webpush", to: "web_push#subscribe", as: :webpush_subscribe
   end
 
   resource :anonymous_block, controller: :anonymous_block, only: %i[create destroy]