Move to auth package in faas-provider

The basic-auth middleware and credentials-loading code has been
moved into the faas-provider project. This has now been brought
back into the faas project via vendoring.

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

gateway/vendor/github.com/openfaas/faas-provider/auth/basic_auth.go

@@ -0,0 +1,26 @@
+// Copyright (c) OpenFaaS Author(s). All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+package auth
+
+import (
+	"net/http"
+)
+
+// DecorateWithBasicAuth enforces basic auth as a middleware with given credentials
+func DecorateWithBasicAuth(next http.HandlerFunc, credentials *BasicAuthCredentials) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+
+		user, password, ok := r.BasicAuth()
+		w.Header().Set("WWW-Authenticate", `Basic realm="Restricted"`)
+
+		if !ok || !(credentials.Password == password && user == credentials.User) {
+
+			w.WriteHeader(http.StatusUnauthorized)
+			w.Write([]byte("invalid credentials"))
+			return
+		}
+
+		next.ServeHTTP(w, r)
+	}
+}