PostgreSQL rules

[atombrella]

Thank you for this ruleset :)

I think you can remove the rule for PostgreSQL single server version. Microsoft/Azure retired this in favor of flexible server.

I don't find rules for the sku_name for azurerm_postgresql_flexible_server. The rules that are generated by the API don't seem to cover this. I can submit a PR for it?
https://learn.microsoft.com/en-us/azure/postgresql/flexible-server/concepts-compute

There are a few open PRs.

[wata727]

Ideally this should be possible to generate automatically from the API spec, but we welcome patches for other useful rules.