Add support for Cassandra API

[markjbrown]

Can you add an option for Cassandra API in the Create "server" workflow?

Could you also change the terminology you use in this create workflow overall? Cosmos is a managed service. There aren't any servers users provision. Maybe easier to separate the workflow from Postgres create workflow.

[fiveisprime]

Cassandra is already an open feature in #207

I believe we just recently switched to use "server" to help customers understand better what's being created. "Account" is a bit confusing. Is there something else we can use that bridges the gap between the two?

[markjbrown]

Ok, great that Cassandra is on your radar.

Every UX for Cosmos refers to this as an account. Portal, PS, CLI, ARM and management SDKs call this an account. It's only VS Code that calls this a server which I think would be a source of confusion.