Boolean type for config options
Booleans itself comes without parsing
parse(any) :: {:ok, boolean} | :error
Booleans itself comes without parsing.
Any integer not equal to 0 treated as true.
0
true
Any string except "0", "no" and "false" (case insensitive) treated as true
"0"
"no"
"false"
For any other values :error returned
:error