When a function is created with the CREATE FUNCTION statement, the
statement handler does all the necessary preparations on its own. The
very same code exists in schema_tables, when the function is loaded on
boot. This patch generalizes both and keeps function language-specific
context creation inside lang/ code.
The creation function returns context via argument reference. It would
have been nicer if it was returned via future<>, but it's not suitable
for future<T> type :(
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
882b2f4e9f