Add call out for ID management versions in identity API (#1163)

* Update create-identity.md

* Update identity-create-alias.md

* Update identity-merge.md

* Update identity-create-alias.md

Author: myronkaifung

reference/Identity API/identities/create-identity.md

@@ -6,6 +6,12 @@ hidden: false
 createdAt: "2021-08-04T20:56:14.330Z"
 updatedAt: "2023-09-26T21:06:37.368Z"
 ---
+[block:callout]
+{
+  "type": "info",
+  "body": "The $identify event payload is only useful for projects using the Original ID Merge system; it has no functionality in other ID management systems. Please review [this section of our documentation](https://docs.mixpanel.com/docs/tracking-methods/id-management/identifying-users#simplified-vs-original-id-merge) for more information."
+}
+[/block]
 
 [block:callout]
 {

reference/Identity API/identities/identity-create-alias.md

@@ -7,6 +7,13 @@ createdAt: "2021-08-04T20:46:15.948Z"
 updatedAt: "2023-09-26T21:06:37.385Z"
 ---
 
+[block:callout]
+{
+  "type": "info",
+  "body": "The $create_alias event payload is only useful for projects using the Original ID Merge system and the Legacy ID Management System; it has no functionality in the Simplified ID Merge system. Please review [this section of our documentation](https://docs.mixpanel.com/docs/tracking-methods/id-management/identifying-users#simplified-vs-original-id-merge) for more information."
+}
+[/block]
+
 [block:callout]
 {
   "type": "info",

reference/Identity API/identities/identity-merge.md

@@ -6,6 +6,12 @@ hidden: false
 createdAt: "2021-08-04T20:46:15.950Z"
 updatedAt: "2023-09-26T21:06:37.416Z"
 ---
+[block:callout]
+{
+  "type": "info",
+  "body": "The $merge event payload is only useful for projects using the Original ID Merge system; it has no functionality in other ID management systems. Please review [this section of our documentation](https://docs.mixpanel.com/docs/tracking-methods/id-management/identifying-users#simplified-vs-original-id-merge) for more information."
+}
+[/block]
 
 [block:callout]
 {