Implement Cassandra Table Assets

[eolivelli]

Summary:

• implement support for the "cassandra-table" and the "cassandra-sink" assets
• see below for the usage of the new assets
• in vector-db-sink, with Cassandra/Astra we now support splitting table-name and keyspace (before it was only "table", that included the keyspace)

Other internal changes:

• renamed AstraDBDataSource to CassandraDataSource, now we support both Astra and Cassandra almost everywhere (query, vector-db-sink and cassandra assets)
• removed the DataSourceConfig object, as it worked only for Astra

This is how Cassandra assets look like:

name: "Write to Astra DB"
topics:
  - name: "input-topic"
    creation-mode: create-if-not-exists
assets:
  - name: "vsearch-keyspace"
    asset-type: "cassandra-keyspace"
    creation-mode: create-if-not-exists
    config:
      keyspace: "products"
      datasource: "CassandraDatasource"
      create-statements:
        - "CREATE KEYSPACE products WITH REPLICATION = {'class' : 'SimpleStrategy','replication_factor' : 1};"
  - name: "products-table"
    asset-type: "cassandra-table"
    creation-mode: create-if-not-exists
    config:
      table-name: "products"
      keyspace: "products"
      datasource: "CassandraDatasource"
      create-statements:
        - "CREATE TABLE IF NOT EXISTS products.products (id int PRIMARY KEY,name TEXT,description TEXT);"
pipeline:
  - name: "Write to Cassandra"
    type: "vector-db-sink"
    input: "input-topic"
    configuration:
      datasource: "AstraDatasource"
      table-name: "products"
      keyspace: "vsearch"
      mapping: "id=value.id,description=value.description,name=value.name"

In this example we declare a "cassandra-keyspace" asset that ensures that the Cassandra keyspace exists, in case it doesn't exit it creates it.

Then we have a "cassandra-table" that creates a table.

Please note that "create-statements" is a list, so you can perform multiple operations, for instance you can create the table and then create an index on a Vector field (or other fields)