vweb: add controllers (#17840)

vlib/vweb/tests/controller_duplicate_server.v

@@ -0,0 +1,41 @@
+module main
+
+import vweb
+import time
+import os
+
+struct App {
+	vweb.Context
+	vweb.Controller
+}
+
+struct Admin {
+	vweb.Context
+}
+
+['/admin/duplicate']
+fn (mut app App) duplicate() vweb.Result {
+	return app.text('duplicate')
+}
+
+fn exit_after_timeout(timeout_in_ms int) {
+	time.sleep(timeout_in_ms * time.millisecond)
+	println('>> webserver: pid: ${os.getpid()}, exiting ...')
+	exit(0)
+}
+
+fn main() {
+	if os.args.len != 3 {
+		panic('Usage: `controller_test_server.exe PORT TIMEOUT_IN_MILLISECONDS`')
+	}
+	http_port := os.args[1].int()
+	assert http_port > 0
+	timeout := os.args[2].int()
+	mut app_dup := &App{
+		controllers: [
+			vweb.controller('/admin', &Admin{}),
+		]
+	}
+
+	vweb.run_at(app_dup, host: 'localhost', port: http_port, family: .ip) or { panic(err) }
+}