Support authentication via CloudSQL Proxy

[hsharrison]

What problem are you facing?

We'd like to connect to a CloudSQL instance by connection string rather than endpoint.

Specifically, we always use Cloud SQL Proxy to connect from GKE, so it would be great if that pattern could be supported here.

How could Crossplane help solve your problem?

Support passing a connection string to provider-sql, in which case launch a CloudSQL Proxy sidecar to provide authentication.