Use boost::core::string_view

[vinniefalco]

We need to deprecate BOOST_BEAST_USE_STD_STRING_VIEW and change the type to use boost::core::string_view

[vinniefalco]

isn't this done?

[sehe]

@vinniefalco

Only partially. We replaced boost::string_view with boost::core::string_view.

I wasn't aware of a desire to also get rid of BEAST_USE_STD_STRING_VIEW - for which I never did impact analysis.

Checking back in history suggests that is no longer a realistic desire to support standalone ASIO. Therefore, I so no immediate reason to avoid tie ourselves to Boost Core string_view. In terms of compatibility it is already the Rosetta Stone.

It seems a little impact analysis is all that's needed here.

[eiderdaus]

The message "BOOST_BEAST_USE_STD_STRING_VIEW is deprecated, use BOOST_NO_CXX17_HDR_STRING_VIEW instead" does not make much sense. Defining or undefining BOOST_NO_CXX17_HDR_STRING_VIEW will not bring back BOOST_BEAST_USE_STD_STRING_VIEW's behavior which has been removed obviously. Also it is my understanding whether BOOST_NO_CXX17_HDR_STRING_VIEW is defined should be determined by Boost's build system and nothing a user should tamper with. A better message would be "BOOST_BEAST_USE_STD_STRING_VIEW does not work anymore, stop using it".