Handle `open` end dates in rights statements

[helrond]

Is your feature request related to a problem? Please describe.

Rights statements coming from Aurora and Aquila might have end dates that are serialized as open. However, ArchivesSpace does not appear to have an "open" boolean, and instead the expectation is that rights statements with no end date will have an open end date.

Describe the solution you'd like

Handle open end dates BEFORE passing data to mapping logic. This keeps the Odin resources and mappings intact and just mutates the data we're passing to those mappings.