Defined in github.com/aws/aws-sdk-go/service/sts/api.go
The format of the name ID, as defined by the Format attribute in the NameID element of the SAML assertion. Typical examples of the format are transient or persistent.
If the format includes the prefix urn:oasis:names:tc:SAML:2.0:nameid-format,
that prefix is removed. For example, urn:oasis:names:tc:SAML:2.0:nameid-format:transient is returned as transient. If the format includes any other prefix, the format is returned with no modifications.