feat: support time_zone for user registration context

authsession/api/public-openapi.yaml

@@ -71,8 +71,8 @@ paths:
       description: |
         Completes a previously issued `challenge_id`, validates the submitted
         verification code, registers the standard base64-encoded raw 32-byte
-        Ed25519 `client_public_key`, and returns the created
-        `device_session_id`.
+        Ed25519 `client_public_key`, validates the submitted IANA
+        `time_zone`, and returns the created `device_session_id`.
       security: []
       requestBody:
         required: true
@@ -86,6 +86,7 @@ paths:
                   challenge_id: challenge-123
                   code: "123456"
                   client_public_key: 11qYAYdk8v3K6Yw8QK6ZlQ2nP4Wm8Cq5g1H0K8vT9no=
+                  time_zone: Europe/Kaliningrad
       responses:
         "200":
           description: The device session was created and is ready for use.
@@ -137,6 +138,7 @@ components:
         - challenge_id
         - code
         - client_public_key
+        - time_zone
       properties:
         challenge_id:
           type: string
@@ -147,6 +149,9 @@ components:
         client_public_key:
           type: string
           description: Standard base64-encoded raw 32-byte Ed25519 public key registered for the new device session.
+        time_zone:
+          type: string
+          description: Client-selected IANA time zone name forwarded as create-only registration context.
     ConfirmEmailCodeResponse:
       type: object
       additionalProperties: false
@@ -201,7 +206,7 @@ components:
       description: |
         Request body or field values are invalid. This includes malformed
         request payloads, invalid confirmation codes, and malformed
-        `client_public_key` values.
+        `client_public_key` or `time_zone` values.
       content:
         application/json:
           schema:
@@ -222,6 +227,11 @@ components:
                 error:
                   code: invalid_client_public_key
                   message: client_public_key is not a valid base64-encoded raw 32-byte Ed25519 public key
+            invalidTimeZone:
+              value:
+                error:
+                  code: invalid_request
+                  message: time_zone must be a valid IANA time zone name
     ChallengeNotFoundError:
       description: The referenced challenge does not exist.
       content: