Add in_response_to field to SAML response (#5805)

Adds a new field in the response of SAML
authentication request, reflecting recent
change in elasticsearch

Closes elastic/elasticsearch#128179

Author: piotrsulkowski-elastic

output/openapi/elasticsearch-openapi.json

@@ -41,5 +41,9 @@ export class Response {
      * The name of the realm where the user was authenticated.
      */
     realm: string
+    /**
+     * The id of the request that initiated the authentication process.
+     */
+    in_response_to?: string
   }
 }

output/schema/schema.json

@@ -8,5 +8,6 @@ value: |-
     "username" : "Bearer",
     "expires_in" : 1200,
     "refresh_token": "mJdXLtmvTUSpoLwMvdBt_w",
-    "realm": "saml1"
+    "realm": "saml1",
+    "in_response_to": "4fee3b046395c4e751011e97f8900b5273d56685"
   }