Middleware (#502)

* API endpoint extensions working.

extensions example.

extensions example.

* Added server.NewEnv and some docs for the API extensions example.

extensions example.

extensions example.

* Uncommented special handler stuff.

* First example of middleware.

easier to use.

* Added a special Middleware context to make middleware easier to use.

* Fix tests.

* Cleanup based on PR comments.

api/server/server.go

@@ -44,6 +44,7 @@ type Server struct {
 
 	specialHandlers []SpecialHandler
 	appListeners    []AppListener
+	middlewares     []Middleware
 	runnerListeners []RunnerListener
 
 	mu           sync.Mutex // protects hotroutes
@@ -95,7 +96,7 @@ func New(ctx context.Context, ds models.Datastore, mq models.MessageQueue, apiUR
 	}
 
 	s.Router.Use(prepareMiddleware(ctx))
-	s.bindHandlers()
+	s.bindHandlers(ctx)
 
 	for _, opt := range opts {
 		opt(s)
@@ -103,6 +104,7 @@ func New(ctx context.Context, ds models.Datastore, mq models.MessageQueue, apiUR
 	return s
 }
 
+// todo: remove this or change name
 func prepareMiddleware(ctx context.Context) gin.HandlerFunc {
 	return func(c *gin.Context) {
 		ctx, _ := common.LoggerWithFields(ctx, extractFields(c))
@@ -239,7 +241,7 @@ func (s *Server) startGears(ctx context.Context) {
 	svr.Serve(ctx)
 }
 
-func (s *Server) bindHandlers() {
+func (s *Server) bindHandlers(ctx context.Context) {
 	engine := s.Router
 
 	engine.GET("/", handlePing)
@@ -247,6 +249,7 @@ func (s *Server) bindHandlers() {
 	engine.GET("/stats", s.handleStats)
 
 	v1 := engine.Group("/v1")
+	v1.Use(s.middlewareWrapperFunc(ctx))
 	{
 		v1.GET("/apps", s.handleAppList)
 		v1.POST("/apps", s.handleAppCreate)