Multiple names for registered objects?

[joshmarshall1]

While updating GroupBy to have register and attach functionality, I found that in the case of Categorical, unique_keys.categories shares the same object as keys.categories so during registration the unique_keys.categories overwrites the reference to keys.categories making a direct call to ``Categorical.attach(name)` unable to locate the required components.

In #1122 I used a workaround to get the components all built, but after discussing with @Ethan-DeBandi99 and @pierce314159 we wanted to open a discussion on if server objects -> registered names should remain 1:1 or if they should allow for 1:many relationships with multiple names able to refer to the same object.

Alternatively if @mhmerrill @reuster986 @ronawho or @bmcdonald3 know of ways to do this already then GroupBy's attach and register might want to be updated to use that.