Adds the magic `frozen_string_literal: true` comment to every file and
enables a Rubocop rule to make sure that it's always going to be there
going forward as well.
See here for more background [1], but the basic idea is that unlike many
other languages, static strings in code are mutable by default. This has
since been acknowledged as not a particularly good idea, and the
intention is to rectify the mistake when Ruby 3 comes out, where all
string literals will be frozen. The `frozen_string_literal` magic
comment was introduced in Ruby 2.3 as a way of easing the transition,
and allows libraries and projects to freeze their literals in advance.
I don't think this is breaking in any way: it's possible that users
might've been pulling out one of are literals somehow and mutating it,
but that would probably not have been useful for anything and would
certainly not be recommended, so I'm quite comfortable pushing this
change through as a minor version.
As discussed in #641.
[1] https://stackoverflow.com/a/37799399
Now that we're powering all test suites with the fixture data that's
generated along with the OpenAPI spec, we don't need this secondary
sample data anymore. Remove all of it except for helpers to simulate
different types of error responses.
* Add support for multiplan subscriptions:
Serialize indexed arrays into hashes with index keys in subscription create, subscription update, and upcoming invoice
Add a SubscriptionItem object that supports creation, deletion, update, listing, and retrieval
* Remove helpers that convert items array to indexed hash
* 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
