Error "No authentication provider found for id: null" when adding execution to an authentication flow via Admin REST API in Keycloak/

Issue

When attempting to add a new execution to an authentication flow in Red Hat Single Sign-On (RH-SSO) or Red Hat Build of Keycloak using the Admin REST API endpoint POST /admin/realms/{realm}/authentication/flows/{flowAlias}/executions/execution, the request fails with the following error:

"error": "No authentication provider found for id: null

This issue occurs when sending a JSON request body that incorrectly specifies the authentication provider. For example, using a payload with the key "authenticator":

 "authenticator": "example-authenticator"

The API documentation may be unclear, listing the required request body as AnyType, leading to confusion about the correct JSON structure.