format() tests

[vinniefalco]

I wrote a format function for the logging that is a lean, slimmed down version of std::format which leans on operator<< to convert things. It needs tests.

[vinniefalco]

seems there are already tests which I forgot that I wrote.... what's the coverage like?

[MungoG]

I created a dummy PR to force the CI to run which should spit out a code coverage report.

[MungoG]

See https://app.codecov.io/gh/cppalliance/beast2/pull/98/blob/include/boost/beast2/format.hpp?dropdown=coverage
We have full coverage apart from appendbuf::overflow which doesn't get called.

[vinniefalco]

how can we make overflow get called and are the tests sufficient, or did I miss something