Enable ssl use for cluster in CassandraIO

[niv-lac]

This PR is to address inability to utilize SSL, as referenced in issue 21223, by surfacing the cluster builder withSSL( SSLOptions sslOptions) method to allow the user to provide SSL configuration. I chose to allow the user to provide SSLOptions to allow different SSL strategies in cases where one user may want client to node encryption and client certificate authentication while another may just want client to node encryption.

Notes:

• First time creating a PR for a non-work related project. Tried to follow the contribution documentation but please let me know if I need to include anything additional or if there are any processes I missed. Thanks.
• Since this PR is surfacing builder ssl functionality from the Datastax driver, I didn't include unit tests to test their functionality.
• Also, I don't believe I would be able to configure SSL on the embedded test cluster.
• These changes have been tested with poc Dataflow job created via Dataflow classic template where truststore cert (self-signed) and password are retrieved at runtime and used to create an SSLContext which is then used to create SSLOptions. The pipeline reads from SQL Server and writes to a DSE 6.8 Cassandra cluster with SSL (TLS protocol) enabled, hosted in GCP.

Please let me know if you have any questions. Thank you.

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[Abacn]

Thanks for the contribution!

[niv-lac]

Thank you!