vweb: adding a vweb.csrf protection module (#15586)

vlib/vweb/csrf/structs.v

@@ -0,0 +1,30 @@
+// This module provides csrf-protection for apps written with libe vweb.
+
+module csrf
+
+import vweb
+import net.http
+
+type CsrfCookie = http.Cookie
+
+interface CheckedApp {}
+
+pub struct App {
+	vweb.Context
+	csrf_cookie_value string
+}
+
+pub struct HttpOnly {
+	http_only bool
+}
+
+struct CsrfError {
+	Error
+	m string
+}
+
+fn (err CsrfError) msg() string {
+	return err.m
+}
+
+// Written by flopetautschnig (floscodes) 2022