Add support of an embedded complex-type for a collection in a given json schema

[yarongilor]

Gemini doesn't support a column which is, for example, a list of UDTs. We would like Gemini to support requested schema that will generate something like:

CREATE KEYSPACE IF NOT EXISTS custom_d1 WITH replication = {'class': 'NetworkTopologyStrategy', 'replication_factor': '1'}  AND durable_writes = true;

CREATE TYPE IF NOT EXISTS custom_d1.post_action (id3 bigint, name3 text, response_type3 tinyint);

CREATE TABLE custom_d1.posts (
    ...
    additions list<frozen<post_action>>
    ...
...
);