CloudSQL support and url overrides in resource

[trevex]

Hi @paultyng ,

I recently stumbled upon this provider and when I was looking into provisioning database instance users with terraform.
On GCP there is an API to create users on CloudSQL instances, however they will be created as "superusers".
For readonly-users or similar, you have to drop down to SQL. By default CloudSQL instances are not directly reachable, but can be reached through a proxy. Luckily the proxy can be embedded directly in Go and even be used as SQL driver.

I went ahead and implemented a minimal provider myself earlier: https://github.com/trevex/terraform-provider-cloudsql

But if you are open to it I can see if I can draft up a PR implementing CloudSQL-support in this provider.

[paultyng]

I'd be happy to see this added, the only concern I would have is testability. Do you know if there is a free version of CloudSQL it could run against or anything like that?

[trevex]

Unfortunately there is no free tier for CloudSQL and no simulator either, so for tests we will require a real instance or alternatively mock the Dialer used underneath. The latter does not sound appealing to me, so I will reach out to my contacts at Google and see if I can organize a free one.

[bitte-ein-bit]

You might want to check the GoCloud approach which would be universal. I've provided a PR in the past to the MySQL provider that I still have on disk hopefully. if you are interested, I could reupload. winebarrel/terraform-provider-mysql#37