Add taggability for SQL Databases

[JustinWilkinson]

The changes in this PR are as follows:

• Add taggability for SQL Databases

Below is a minimal example configuration that includes the new features, which can be used to deploy to Azure:

sqlDb {
    name "db"
    link_to_unmanaged_server (Arm.Sql.servers.resourceId("server")) (ResourceName "server-pool")
    add_tags [ "key", "value" ]
}