Kefu Chai c14c70b89d utils: UUID: specialize fmt::formatter for UUID and tagged_uuid<> ...

this is a part of a series to migrating from `operator<<(ostream&, ..)`
based formatting to fmtlib based formatting. the goal here is to enable
fmtlib to print UUID without using ostream<<. also, this change reimplements
some formatting helpers using fmtlib for better performance and less
dependencies on operator<<(), but we cannot drop it at this moment,
as quite a few caller sites are still using operator<<(ostream&, const UUID&)
and operator<<(ostream&, tagged_uuid<T>&). we will address them separately.

* add fmt::formatter<UUID>
* add fmt::formatter<tagged_uuid<T>>
* implement UUID::to_string() using fmt::to_string()
* implement operator<<(std::ostream&, const UUID&) with fmt::print(),
  this should help to improve the performance when printing uuid, as
  fmt::print() does not materialize a string when printing the uuid.

Refs #13245

Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>

2023-03-20 14:25:45 +08:00

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