Add /system/namespaces endpoint

This is being added to enable the UI/CLI to list valid
OpenFaaS function namespaces before then sending the namespace
as a query to other endpoints.

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>

serve.go

@@ -65,6 +65,8 @@ func Serve(handlers *types.FaaSHandlers, config *types.FaaSConfig) {
 	r.HandleFunc("/system/secrets", handlers.SecretHandler).Methods(http.MethodGet, http.MethodPut, http.MethodPost, http.MethodDelete)
 	r.HandleFunc("/system/logs", handlers.LogHandler).Methods(http.MethodGet)
 
+	r.HandleFunc("/system/namespaces", handlers.ListNamespaceHandler).Methods("GET")
+
 	// Open endpoints
 	r.HandleFunc("/function/{name:["+NameExpression+"]+}", handlers.FunctionProxy)
 	r.HandleFunc("/function/{name:["+NameExpression+"]+}/", handlers.FunctionProxy)

types/config.go

@@ -7,22 +7,25 @@ import (
 
 // FaaSHandlers provide handlers for OpenFaaS
 type FaaSHandlers struct {
-	FunctionReader http.HandlerFunc
-	DeployHandler  http.HandlerFunc
 	// FunctionProxy provides the function invocation proxy logic.  Use proxy.NewHandlerFunc to
 	// use the standard OpenFaaS proxy implementation or provide completely custom proxy logic.
-	FunctionProxy  http.HandlerFunc
+	FunctionProxy http.HandlerFunc
+
+	FunctionReader http.HandlerFunc
+	DeployHandler  http.HandlerFunc
+
 	DeleteHandler  http.HandlerFunc
 	ReplicaReader  http.HandlerFunc
 	ReplicaUpdater http.HandlerFunc
 	SecretHandler  http.HandlerFunc
 	// LogHandler provides streaming json logs of functions
 	LogHandler http.HandlerFunc
 
-	// Optional: Update an existing function
-	UpdateHandler http.HandlerFunc
-	HealthHandler http.HandlerFunc
-	InfoHandler   http.HandlerFunc
+	// UpdateHandler an existing function/service
+	UpdateHandler        http.HandlerFunc
+	HealthHandler        http.HandlerFunc
+	InfoHandler          http.HandlerFunc
+	ListNamespaceHandler http.HandlerFunc
 }
 
 // FaaSConfig set config for HTTP handlers