Since #433, saving API resources nested under other API resources has
not been the default. Instead, any instances where this should occur
have been special cased with specific method implementations that would
set the `#save_with_parent` flag when a field is written.
This ended up causing some problems because as seen in #457, because
places that we need to do this aren't well vetted, some were forgotten.
This makes implementation of new fields that need this behavior simpler
by implementing a `.save_nested_resource` metraprogramming method on the
`APIResource` class. This can be called as necessary by any concrete API
resource implementations.
We replace existing implementatinos and also add one to `Subscription`,
which had previously been suffering from a similar problem where its
`#source` had not received a special case.
* 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
* allow subs to be retrieved & created with new v1/subs API endpoint
* edit tests to check for url
* fix customer subscription URLs to go through v1/customers
I'm not sure exactly what changed here (did we change the `$VERBOSE`
setting?), but I'm not seeing a whole lot of warnings when running the
test suites locally and in CI. For example:
```
Started
........................................./home/travis/build/stripe/stripe-ruby/lib/stripe/api_operations/list.rb:6: warning: instance variable @opts not initialized
............../home/travis/build/stripe/stripe-ruby/lib/stripe/api_operations/list.rb:6: warning: instance variable @opts not initialized
../home/travis/build/stripe/stripe-ruby/lib/stripe/api_operations/list.rb:6: warning: instance variable @opts not initialized
......../home/travis/build/stripe/stripe-ruby/lib/stripe/api_operations/list.rb:6: warning: instance variable @opts not initialized
.../home/travis/build/stripe/stripe-ruby/lib/stripe/api_operations/list.rb:6: warning: instance variable @opts not initialized
........./home/travis/build/stripe/stripe-ruby/lib/stripe/api_operations/list.rb:6: warning: instance variable @opts not initialized
...
..../home/travis/build/stripe/stripe-ruby/lib/stripe/api_operations/list.rb:6: warning: instance variable @opts not initialized
....../home/travis/build/stripe/stripe-ruby/lib/stripe/api_operations/list.rb:6: warning: instance variable @opts not initialized
..../home/travis/build/stripe/stripe-ruby/lib/stripe/api_operations/list.rb:6: warning: instance variable @opts not initialized
......./home/travis/build/stripe/stripe-ruby/lib/stripe/api_operations/list.rb:6: warning: instance variable @opts not initialized
........./home/travis/build/stripe/stripe-ruby/lib/stripe/api_operations/list.rb:6: warning: instance variable @opts not initialized
........../home/travis/build/stripe/stripe-ruby/lib/stripe/api_operations/list.rb:6: warning: instance variable @opts not initialized
................./home/travis/build/stripe/stripe-ruby/lib/stripe/api_operations/list.rb:6: warning: instance variable @opts not initialized
.../home/travis/build/stripe/stripe-ruby/lib/stripe/api_operations/list.rb:6: warning: instance variable @opts not initialized
..../home/travis/build/stripe/stripe-ruby/lib/stripe/api_operations/list.rb:6: warning: instance variable @opts not initialized
....../home/travis/build/stripe/stripe-ruby/lib/stripe/api_operations/list.rb:6: warning: instance variable @opts not initialized
..........
........./home/travis/build/stripe/stripe-ruby/lib/stripe/api_operations/list.rb:6: warning: instance variable @opts not initialized
....../home/travis/build/stripe/stripe-ruby/lib/stripe/api_operations/list.rb:6: warning: instance variable @opts not initialized
......../home/travis/build/stripe/stripe-ruby/lib/stripe/api_operations/list.rb:6: warning: instance variable @opts not initialized
......../home/travis/build/stripe/stripe-ruby/lib/stripe/api_operations/list.rb:6: warning: instance variable @opts not initialized
............./home/travis/build/stripe/stripe-ruby/lib/stripe/stripe_object.rb:35: warning: instance variable @values not initialized
./home/travis/build/stripe/stripe-ruby/lib/stripe/stripe_object.rb:35: warning: instance variable @values not initialized
...................../home/travis/build/stripe/stripe-ruby/lib/stripe/transfer.rb:8: warning: instance variable @api_key not initialized
..............
..
Finished in 0.785621037 seconds.
```
Most of these are due to unused or uninitialized variables. This patch
fixes all warnings by fixing offending code.
As discussed in #325, this deprecates the public visibility of
`#refresh_from` (by renaming it). It also adds some deprecation
infrastructure to produce warnings when it's used.
