Name:  UsernameCaseMapped.

Base Class:  IdentifierClass.

Applicability:  Usernames in security and application protocols.

Replaces:  The SASLprep profile of Stringprep.

Width-Mapping Rule:  Map fullwidth and halfwidth code points to their
decomposition mappings.

Additional Mapping Rule:  None.

Case-Mapping Rule:  Map uppercase and titlecase code points to
lowercase.

Normalization Rule:  NFC.

Directionality Rule:  The "Bidi Rule" defined in RFC 5893 applies.

Enforcement:  To be defined by security or application protocols that
use this profile.

Specification: RFC8265 Section 3.3.