Add authentication sub-namespace to user

CHANGELOG.md

@@ -7,6 +7,8 @@
 
 <!-- next version -->
 
+- `user`: Add `anonymous_id` (#1146)
+
 ## v1.26.0
 
 ### 🛑 Breaking changes 🛑

model/registry/user.yaml

@@ -28,8 +28,14 @@ groups:
         type: string
         stability: experimental
         brief: >
-          Unique identifier of the user.
+          Unique identifier of an authenticated user.
         examples: ['S-1-5-21-202424912787-2692429404-2351956786-1000']
+      - anonymous_id
+        type: string
+        stability: experimental
+        brief: >
+          Unique identifier of an anonymous user who interacts with a system or service without providing personal information or authentication credentials. It allows the system to track user activity while maintaining anonymity.
+        examples: ['QdH5CAWJgqVT4rOr0qtumf']
       - id: name
         type: string
         stability: experimental