Accepts a login outcome event for a given identity and registered user.
Records whether a login attempt was successful or failed, enabling downstream
risk model enrichment and account defense features.

The request body must contain an action field indicating the login outcome.

Test Cases:

To test this endpoint, you can use the example identity_id values below. Other arguments are ignored.
Both test cases return an empty HTTP 200 response on success.

For a successful login outcome:

  POST /v6/sessions/example_login_action_successful/users/example_registered_user_id
  { "action": "SUCCESSFUL_LOGIN" }

For a failed login outcome:

  POST /v6/sessions/example_login_action_failed/users/example_registered_user_id
  { "action": "FAILED_LOGIN" }