Aliases are defined in the configuration file under the `aliases` key.
The configuration is a map of alias name to command. When we run the
command the we just do a literal replacement of the alias with the
string.
So if we have:
```yaml
aliases:
console: app exec -r console -i --reuse "rails console"
```
Then running `kamal console -r workers` will run the command
```sh
$ kamal app exec -r console -i --reuse "rails console" -r workers
```
Because of the order Thor parses the arguments, this allows us to
override the role from the alias command.
There might be cases where we need to munge the command a bit more but
that would involve getting into Thor command parsing internals,
which are complicated and possibly subject to change.
There's a chance that your aliases could conflict with future built-in
commands, but there's not likely to be many of those and if it happens
you'll get a validation error when you upgrade.
Thanks to @dhnaranjo for the idea!
b8af719bb7