Introduce support for droplet autoscaler

[asaha2]

Droplet autoscaler is currently in closed alpha and enabled for select customer.

Nit change also includes marking the new load balancer feature flags as visible in the cli text (now that these features are available since GA).

TODO:

• test compiled binary
• add unit tests

[asaha2]

cc @andrewsomething when you have a chance 🙏

[andrewsomething]

Overall this looks great. There are some minor copy suggestions inline.

The one issue I'm seeing is with the Displayable implementation. Rather than using a single type with switch statements, each should be its own type. This will allow you to remove the format flags that have been added manually. When the displayer is implemented correctly, the flag is added automatically. The help output will also have the column names populated automatically.

It would also be great to get some additional help information into the command long descriptions, but that can follow later. If there is someone on the product docs team working on this release, they might be able help there.

[andrewsomething]

Thanks for the updates! This is very close. Though I did notice that you changed the commands that require an autoscale pool ID from using a positional argument to an --id flag. Any particular reason for that?

Most doctl commands that act on an existing resource tag the ID as a positional argument. For example: doctl compute droplet get <id> Unless there is a specific reason not too, it would be more consistent to do so here too.

[asaha2]

@andrewsomething Yeah should've perhaps checked in with you on this: it just seemed counter-intuitive that we accept --id as per command help text, but if we run it with --id=<id> we seem to get a Error: (droplet-autoscale.list-members) command is missing required arguments E.g.:

asaha@C02FLDHYMD6M:doctl ./builds/doctl -t $DIGITALOCEAN_TOKEN -u https://api.s2r1.internal.digitalocean.com compute droplet-autoscale list-members -h
List all members of a Droplet autoscale pool

Usage:
  doctl compute droplet-autoscale list-members [flags]

Flags:
      --format ID   Columns for output in a comma-separated list. Possible values: ID, `Status`, `Health Status`, `Unhealthy Reason`, `CPU Util`, `Mem Util`.
  -h, --help        help for list-members
      --id string   ID of the Droplet autoscale pool (required)
      --no-header   Return raw data with no headers
asaha@C02FLDHYMD6M:doctl ./builds/doctl -t $DIGITALOCEAN_TOKEN -u https://api.s2r1.internal.digitalocean.com compute droplet-autoscale list-members --id=41fd76b0-3487-4ae6-8979-d26da4b7b122
Error: (droplet-autoscale.list-members) command is missing required arguments
asaha@C02FLDHYMD6M:doctl ./builds/doctl -t $DIGITALOCEAN_TOKEN -u https://api.s2r1.internal.digitalocean.com compute droplet-autoscale list-members 41fd76b0-3487-4ae6-8979-d26da4b7b122
ID          Status    Health Status    Unhealthy Reason    CPU Util    Mem Util
11735085    active    healthy                              0.001083    0.366714
11735086    active    healthy                              0.000704    0.382897

[andrewsomething]

👍 LGTM!