Support the new form utils in the OAuth App and WebHook API resources.
Review Request #10376 — Created Jan. 8, 2019 and submitted
This updates the existing OAuth App and WebHook API resources to use the
new form API utilities in Djblets, reducing the amount of code needed in
both of those resources.
It also improves Review Board's wrappers around the form utilities,
allowing our existing extra_data import support to work with the new
Unit tests pass.