[Feature Request] Add Enums of queryable/selectable attributes for Messages/Folders/Contacts/etc.

[matthewgdv]

Hi there,

This should be pretty simple request, but it may be a bit annoying and time-consuming.

Basically, it would be dead useful if there were Enums provided in the library so that users could use autocompletion tools (e.g. Jedi) to get a list of attributes that can go into the Query.on_attribute() method, rather than having to sift through the docs to find out what they are.

In particular, there are funny rules about which attributes are allowed in filter clauses, which can lead to a lot of trial and error. This would be avoided if there was, for example, a FilterableMessageAttribute Enum, which only had as its members the attributes that the REST API accepts for filter clauses.

That said, as a starting point, even just simple MessageAttribute, ContactAttribute, MessageFolderAttribute, etc. Enums would increase the utility of the library by a lot.

Would be cool to see something like this implemented, but I totally get it if there are greater priorities.

Cheers for the awesome library!