A registered extension value (tags 0xF0..0xFF).

Extension types are the forward-compatible escape hatch of the BTOON wire format: an extension value is encoded as its tag, a length prefix and the raw payload, so any decoder can skip an unimplemented extension instead of failing. The payload's internal layout is defined by the extension's registration.

Tag ranges:

• 0xF0–0xF7 — experimental / vendor-specific
• 0xF8–0xFB — official (registered with the maintainers)
• 0xFC–0xFF — private / application-local

Examples

iex> ext = Btoon.Extension.new(0xF0, <<1, 2, 3>>)
iex> Btoon.decode!(Btoon.encode!(ext))
%Btoon.Extension{tag: 240, data: <<1, 2, 3>>}