so that it is accessible from its caller. if we enforce the
compile-time format string check, the formatter would need the access to
the specialization of `fmt::formatter` of the arguments being foramtted.
to be prepared for this change, let's move the `fmt::formatter`
specialization up, otherwise we'd have following error after switching
to the compile-time format string check introduced by a recent seastar
change:
```
In file included from ./auth/authenticator.hh:22: ./auth/authentication_options.hh:50:49: error: call to consteval function 'fmt::basic_format_string<char, auth::authentication_option &>::basic_format_string<
char[32], 0>' is not a constant expression
50 | : std::invalid_argument(fmt::format("The {} option is not supported.", k)) {
| ^ ./auth/authentication_options.hh:57:13: error: explicit specialization of 'fmt::formatter<auth::authentication_option>' after instantiation
57 | struct fmt::formatter<auth::authentication_option> : fmt::formatter<string_view> {
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/fmt/base.h:1228:17: note: implicit instantiation first required here
1228 | -> decltype(typename Context::template formatter_type<T>().format(
| ^
In file included from replica/distributed_loader.cc:30:
```
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closesscylladb/scylladb#20447