implement auth using Auth0

internal/site/cookie.go

@@ -0,0 +1,11 @@
+package site
+
+import "net/http"
+
+func deleteCookieInResponse(w http.ResponseWriter, name string) {
+	w.Header().Set("Set-Cookie", (&http.Cookie{
+		Name:   name,
+		Path:   "/",
+		MaxAge: -1, // expire the cookie
+	}).String())
+}