Add AstraDB Support

[waleedzeb]

AstraDB is a fully managed serverless Cassandra database. The service manages everything and provides a cost-effective serverless cost structure.

Has anyone tried this?

[vtslab]

Thanks for bringing this up. If you want to discuss this further, you can do so in the discussions section or on the users list.

AstraDB states that it works with Cassandra 3.11 clients (https://docs.datastax.com/en/astra/docs/datastax-astra-faq.html). JanusGraph supports Cassandra 3.11 (https://docs.janusgraph.org/changelog/#version-compatibility).
Although the JanusGraph website mentions ScyllaDB as a separate storage backend, there are many options for managed Cassandra services, so a list of these would not make things clearer and would be out of date soon.