Instead of lengthy blurbs, switch to single-line, machine-readable
standardized (https://spdx.dev) license identifiers. The Linux kernel
switched long ago, so there is strong precedent.
Three cases are handled: AGPL-only, Apache-only, and dual licensed.
For the latter case, I chose (AGPL-3.0-or-later and Apache-2.0),
reasoning that our changes are extensive enough to apply our license.
The changes we applied mechanically with a script, except to
licenses/README.md.
Closes#9937
The overloaded_functor class template can be used to encompass multiple
lambdas accepting different types into a single callable object that can
be used with any of those types.
One application is visitors for std::variant where different handling is
required for different types.
Signed-off-by: Vladimir Krivopalov <vladimir@scylladb.com>
