I wanted to see what fixing Rubocop TODOs was like, so I tried to
eliminate all the easy ones. Most of these were pretty easy, and the
changes required are relatively minimal.
Some of the stuff left is harder. Pretty much everything under
`Metrics/*` is going to be a pretty big yak shave. A few of the others
are just going to need a little more work (e.g. `Style/ClassVars` and
`Style/GuardClause`). Going to stop here for now.
As described in #481, adding a protected field like `legal_entity` as
part of an update API operation can cause some issues like a custom
encoding scheme not being considered and special handling around empty
values being ignored.
As a an easy fix for this, let's disallow access to protected fields in
the same way that we disallow them from being set directly on an
instance of a given model.
Helps address (but is not a complete fix for) #481.
* Rename the `Update` operation to `Save`
* Add the `update` class method to all saveable resources
* Add tests for update method
* Add tests for plans, invoice items, and application fees
