Dynamic types for module arguments

Hi Rhys,

The original ssl_cert_reqs argument is a string. These string values
map to the new boolean values.

I basically want to map the strings as follows..

CERT_NONE - True
CERT_REQUIRED - False

But also allow boolean values to be accepted.

maybe doing `type: raw` with `choices: [CET_NONE, CERT_REQUIRED, true,
false]` would work.

Alternatively, keep the old option, make the new and old option
mutually_exclusive, and eventually deprecate the old one. (While both
exist, none can have a default, so you need to document the actual default
manually in the documentation, and not with `default:`.)

I think having two separate options is probably the best way to handle
this particularly strange one :slight_smile:

Cheers,
Felix