FEATURE: add user_session_refreshed trigger (#9412)

Trigger an event for plugins to consume when a user session is refreshed.

This allows external auth to be notified about account activity, and be
able to take action such as use oauth refresh tokens to keep oauth
tokens valid.

lib/auth/default_current_user_provider.rb

@@ -148,6 +148,7 @@ class Auth::DefaultCurrentUserProvider
                                client_ip: @request.ip,
                                path: @env['REQUEST_PATH'])
           cookies[TOKEN_COOKIE] = cookie_hash(@user_token.unhashed_auth_token)
+          DiscourseEvent.trigger(:user_session_refreshed, user)
         end
       end
     end

spec/components/auth/default_current_user_provider_spec.rb

@@ -595,6 +595,43 @@ describe Auth::DefaultCurrentUserProvider do
 
   end
 
+  context "events" do
+    before do
+      @refreshes = 0
+
+      @increase_refreshes = -> (user) { @refreshes += 1 }
+      DiscourseEvent.on(:user_session_refreshed, &@increase_refreshes)
+    end
+
+    after do
+      DiscourseEvent.off(:user_session_refreshed, &@increase_refreshes)
+    end
+
+    it "fires event when updating last seen" do
+      user = Fabricate(:user)
+      @provider = provider('/')
+      cookies = {}
+      @provider.log_on_user(user, {}, cookies)
+      unhashed_token = cookies["_t"][:value]
+      freeze_time 20.minutes.from_now
+      provider2 = provider("/", "HTTP_COOKIE" => "_t=#{unhashed_token}")
+      provider2.refresh_session(user, {}, {})
+      expect(@refreshes).to eq(1)
+    end
+
+    it "does not fire an event when last seen does not update" do
+      user = Fabricate(:user)
+      @provider = provider('/')
+      cookies = {}
+      @provider.log_on_user(user, {}, cookies)
+      unhashed_token = cookies["_t"][:value]
+      freeze_time 2.minutes.from_now
+      provider2 = provider("/", "HTTP_COOKIE" => "_t=#{unhashed_token}")
+      provider2.refresh_session(user, {}, {})
+      expect(@refreshes).to eq(0)
+    end
+  end
+
   context "rate limiting" do
 
     before do