Update extend() to take optional arguments and Spina options.
Review Request #13523 — Created Feb. 6, 2024 and submitted
.extend()method for classes no longer requires any arguments. It
had previously required both prototype and static attributes, which
behaved differently from Backbone's version.
It also now takes a third option for Spina options. These are the same
arguments found in the
@spinadecorator. It's really there for some
unit testing, but can be useful in transitioning some code.
Spina and Review Board unit tests pass.
Tested this in an upcoming change.