Add redirect_url field to track where a visitor is redirected for a visit

docs/async-api/async-api.json

@@ -247,6 +247,11 @@
                         "type": "string",
                         "nullable": true,
                         "description": "The originally visited URL that triggered the tracking of this visit"
+                    },
+                    "redirectUrl": {
+                        "type": "string",
+                        "nullable":  true,
+                        "description": "The URL to which the visitor was redirected"
                     }
                 },
                 "example": {

docs/swagger/definitions/Visit.json

@@ -25,6 +25,10 @@
         "visitedUrl": {
             "type": ["string", "null"],
             "description": "The originally visited URL that triggered the tracking of this visit"
+        },
+        "redirectUrl": {
+            "type": ["string", "null"],
+            "description": "The URL to which the visitor was redirected"
         }
     }
 }