feat: add some Radius protocol code (#2351)

* feat: add radius server

* feat: parse org from packet

* feat: add comment

* Update main.go

---------

Co-authored-by: hsluoyz <hsluoyz@qq.com>

radius/util.go

@@ -0,0 +1,40 @@
+// Copyright 2023 The Casdoor Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package radius
+
+import (
+	"layeh.com/radius"
+	"layeh.com/radius/rfc2865"
+)
+
+const (
+	OrganizationVendorID = uint32(100)
+)
+
+func parseOrganization(p *radius.Packet) string {
+	for _, avp := range p.Attributes {
+		if avp.Type == rfc2865.VendorSpecific_Type {
+			attr := avp.Attribute
+			vendorId, value, err := radius.VendorSpecific(attr)
+			if err != nil {
+				return ""
+			}
+			if vendorId == OrganizationVendorID {
+				return string(value)
+			}
+		}
+	}
+	return ""
+}