The method `functions::get` is used to get the `functions::function` object
of the CQL function called using `expr::function_call`.
Until now `functions::get` required the caller to pass both the keyspace
and the column family.
The keyspace argument is always needed, as every CQL function belongs
to some keyspace, but the column family isn't used in most cases.
The only case where having the column family is really required
is the `token()` function. Each variant of the `token()` function
belongs to some table, as the arguments to the function are the
consecutive partition key columns.
Let's make the column family argument optional. In most cases
the function will work without information about column family.
In case of the `token()` function there's gonna be a check
and it will throw an exception if the argument is nullopt.
Signed-off-by: Jan Ciolek <jan.ciolek@scylladb.com>
15ed83adbc