Requires "workaround" fix for schema_registry and frozen_mutation, since
the former is a free-float thread local, and the latter is a pure data
carrier. frozen_schema can take a parameter for unfreeze, but schema
registry requires being told which the system extensions are.
Original IDL generated code was hardcoded to always use bytes_ostream.
This patch makes the output stream a template parameter so that any
valid output stream can be used.
Unfortunately, making IDL writers generic requires updates in the code
that uses them, this is fixed in C++17 which would be able to deduce the
parameter in most cases.
This patch allows a view schema to be frozen. To unfreeze such a
schema, we add an is_view attribute to the schema idl.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
