Add Cosmos database resource.

[mitchdenny]

This PR adds support for AddDatabase(...) on Cosmos database resources.

Microsoft Reviewers: Open in CodeFlow

Usage:

var builder = DistributedApplication.CreateBuilder(args)
var account = builder.AddCosmosDB("myaccount");
var db = account.AddDatabase("imports");

The manifest will look like this:

{
  "resources": {
    "myaccount": {
      "type": "azure.cosmosdb.account.v0"
    },
    "imports": {
      "type": "azure.cosmosdb.database.v0",
      "parent": "myaccount"
    }
  }
}

The expectation is that a deployment tool that supports these resource types would create the database as well.

[davidfowl]

Can you update the provisioner as well?

[Pilchie]

This is essentially exactly what I had in one of the iterations of my PR ;)

[mitchdenny]

Yeah at the time I didn't quite realize just how painful it is to create a database when using managed identity with the data plane SDK.

[Pilchie]

Note that I think in the long term we're going to loosen that up and support it in the data plane SDK, but that's probably a next semester work item.

[mitchdenny]

Can you update the provisioner as well?

Provisioner updated.

[davidfowl]

You could do a single pass over the set of databases but I'm not concerned about performance 😄