Now that named_value::value_as_json() exists, make use of it to report the
current value of a configuration variable via the REST API, instead of
_make_config_values().
Many headers don't really need to include database.hh, the include can
be replaced by forward declarations and/or including the actually needed
headers directly. Some headers don't need this include at all.
Each header was verified to be compilable on its own after the change,
by including it into an empty `.cc` file and compiling it. `.cc` files
that used to get `database.hh` through headers that no longer include it
were changed to include it themselves.
The config API is created dynamically from the config. This mean that
the swagger definition file will contain the description and types based on the
configuration.
The config.json file is used by the code generator to define a path that is
used to register the handler function.
Signed-off-by: Amnon Heiman <amnon@scylladb.com>
