The ID of the entity. For Google-managed entities, the id should be the email address of an existing group or user. Email addresses need to adhere to name guidelines for users and groups. For external-identity-mapped entities, the id must be a string conforming to the Identity Source's requirements. Must be unique within a namespace.

The namespace in which the entity exists. If not specified, the EntityKey represents a Google-managed entity such as a Google user or a Google Group. If specified, the EntityKey represents an external-identity-mapped group. The namespace must correspond to an identity source created in Admin Console and must be in the form of identitysources/{identity_source}.