A federated identity system is composed of three main components. Which of the following is NOT one of the three main components?

The Identity Provider is a core component responsible for authenticating users and asserting their identity.

The User (or subject) is a core component representing the individual requesting access to resources.

The Relying Party (or Service Provider) is a core component that trusts the Identity Provider's assertions to grant access to resources.

An API (Application Programming Interface) is a set of defined methods for software components to communicate, which may be utilized within or between the components of a federated identity system (e.g., using SAML or OIDC APIs) but is not considered one of the three primary architectural roles or entities in the system itself.