v3: ForEachZone helper and logging

[kobajagi]

Example usage of ForEachZone and logging with builtin Logger implementation (StandardLogger):

func main() {
    client, err := exoscale.DefaultClient(
        exoscale.ClientOptWithCredentialsFromEnv(),
        exoscale.ClientOptWithLogger(exoscale.NewStandardLogger(os.Stdout, true)),
    )
    if err != nil {
        panic(err)
    }

    client.ForEachZone(func(c *exoscale.Client, zone oapi.ZoneName) {
        l, err := c.Compute().LoadBalancers().Get(context.Background(), <id>)
        if err != nil {
            fmt.Println(err)
        } else {
            fmt.Println(l)
        }
    })
}

[shortcut-integration[bot]]

This pull request has been linked to Shortcut Story #71887: Additional client middlewares.

[sauterp]

Could it be useful to have an optional argument for ForEachZone that allows users to specify a subset of the zones? It could be a list of zones. Or maybe we could use the option pattern, so that you can for example use v3.SwissZones. Just an idea.

[kobajagi]

Could it be useful to have an optional argument for ForEachZone that allows users to specify a subset of the zones?

Idk if that is the usecase that justifies extra code. Helpers should solve common problems, zones subset iteration doesn't sound common (i cannot think of any usage internally). I'd left it for consumers to implemen.