Update dhcpv6-relay yang model (#14144)

Why I did it
Add interface-id in dhcpv6-relay yang model

How I did it
Add interface-id option and corresponding UT. Updated configuration.md

How to verify it
kellyyeh@kellyyeh:~/sonic-buildimage/src/sonic-yang-models$ pyang -Vf tree -p /usr/local/share/yang/modules/ietf ./yang-models/sonic-dhcpv6-relay.yang

src/sonic-yang-models/doc/Configuration.md

@@ -24,7 +24,8 @@ Table of Contents
          * [Data Plane L3 Interfaces](#data-plane-l3-interfaces)  
          * [DEFAULT_LOSSLESS_BUFFER_PARAMETER](#DEFAULT_LOSSLESS_BUFFER_PARAMETER)  
          * [Device Metadata](#device-metadata)  
-         * [Device neighbor metada](#device-neighbor-metada)  
+         * [Device neighbor metada](#device-neighbor-metada)
+         * [DHCP_RELAY](#dhcp_relay)
          * [DSCP_TO_TC_MAP](#dscp_to_tc_map)  
          * [FLEX_COUNTER_TABLE](#flex_counter_table)  
          * [KDUMP](#kdump)  
@@ -865,6 +866,22 @@ instance is supported in SONiC.
 
 ```
 
+### DHCP_RELAY
+
+```
+{
+"DHCP_RELAY": {
+    "dhcpv6_servers": [
+        "fc02:2000::1",
+        "fc02:2000::2",
+        "fc02:2000::3",
+        "fc02:2000::4"
+    ],
+    "rfc6939_support": "true",
+    "interface_id": "true"
+}
+
+```
 
 ### DSCP_TO_TC_MAP
 ```

src/sonic-yang-models/tests/files/sample_config_db.json

@@ -1628,13 +1628,15 @@
                 "dhcpv6_servers": [
                     "2a04:5555:41::11"
                 ],
-                "rfc6939_support": "true"
+                "rfc6939_support": "true",
+                "interface_id": "true"
             },
             "Vlan777": {
                 "dhcpv6_servers": [
                     "2a04:5555:41::11"
                 ],
-                "rfc6939_support": "true"
+                "rfc6939_support": "true",
+                "interface_id": "true"
             }
         },
         "SCHEDULER": {

src/sonic-yang-models/tests/yang_model_tests/tests/dhcpv6_relay.json

@@ -5,5 +5,9 @@
     },
     "DHCPV6_SERVER_VALID_FORMAT": {
         "desc": "Add dhcpv6_server in correct format."
+    },
+    "DHCPv6_OPTION_WITH_INVALID_BOOLEAN_TYPE": {
+        "desc": "Add dhcpv6 option with invalid option boolean types.",
+        "eStrKey": "Pattern"
     }
 }

src/sonic-yang-models/tests/yang_model_tests/tests_config/dhcpv6_relay.json

@@ -76,11 +76,25 @@
                             "2001:1::2"
                         ],
                         "rfc6939_support": "true",
-
+                        "name": "Vlan400",
+                        "interface_id": "true",
                         "name": "Vlan400"
                     }
                 ]
             }
         }
+    },
+    "DHCPv6_OPTION_WITH_INVALID_BOOLEAN_TYPE": {
+        "sonic-dhcpv6-relay:sonic-dhcpv6-relay": {
+            "sonic-dhcpv6-relay:DHCP_RELAY": {
+                "DHCP_RELAY_LIST": [
+                    {
+                        "name": "Vlan500",
+                        "rfc6939_support": "False",
+                        "interface_id": "False"
+                    }
+                ]
+            }
+        }
     }
 }

src/sonic-yang-models/yang-models/sonic-dhcpv6-relay.yang

@@ -34,15 +34,24 @@ module sonic-dhcpv6-relay {
 					type string;
 				}
 
-                                leaf-list dhcpv6_servers {
+				leaf-list dhcpv6_servers {
-                                        description "Configure the dhcp v6 servers";
+					description "Configure the dhcp v6 servers";
-                                        type inet:ipv6-address;
+					type inet:ipv6-address;
-                                }
+				}
 
-                                leaf rfc6939_support {
+				leaf rfc6939_support {
-                                        description "Set rfc6939 for the relay";
+					description "Set rfc6939 for the relay";
-                                        type boolean;
+					type string {
-                                }
+						pattern "false|true";
+					}
+				}
+
+				leaf interface_id {
+					description "Enable interface ID insertion in relayed messages";
+					type string {
+						pattern "false|true";
+					}
+				}
 			}
 			/* end of VLAN_LIST */
 		}