Add "Enumerated" and "Unrepresentable" domains?

[jsadler2]

If I am understanding how this package works, it can only have "Range Domains" (rdom) in the entity attribute description:

https://github.com/USGS-R/meddle/blob/3924c5a8a8c710d70fe06aaec37579bc4df17874/inst/extdata/FGDC_template.mustache#L215

In the current data-release I am working on, the reviewer, Janet Barclay, suggested that some of my attributes would be better represented by either an "Enumerated Domain" (edom) or an "Unrepresentable Domain" (udom). I agree with her.

The attributes she suggested this for were

1. usgs site numbers for the "Unrepresentable Domain," since the not on a continuous scale and they are actually just ids
2. usgs daily value verification code for "Enumerated Domain," since there are a finite set of possible choices and each choice has a certain meaning

Here's what the Enumerated Domain definitions could look like (and the Attribute Definition could drop the definitions of the different codes):

It would be nice to have the option of specifying these other domains in meddle. Is that supported already? It could be that I just missed it.