Add support for SetupIntent

[moomerman]

This PR adds support for the Stripe SetupIntent object.

• Add SetupIntent module and tests
• Update stripe-mock to latest version for /setup-intents endpoint support.

[coveralls]

Coverage increased (+0.2%) to 88.456% when pulling d5c867b on moomerman:feature/setup-intents into ffef07d on code-corps:master.

[snewcomer]

Tests are fixed! Mind merging in master?

[snewcomer]

Great job! Just a quick review and everything looks pretty close to good!

[mtoeltsch]

Hi guys,
quick comment:
The Stripe.Subscription is missing the field 'pending_setup_intent'.

[moomerman]

Thanks, I'll have look at these. It seems they're still developing it, the list option wasn't there when I implemented it!

[snewcomer]

@moomerman Let me know if you have time to round this one out this week! Looking to release 2.5 by the end of the week.

[doughsay]

Hi everyone, what are the chances we can get this included soon? The EU SCA deadline is fast approaching on September 14th, and we need to use the SetupIntents API to properly support it. 😅 For now, I'm going to attempt to use the branch directly, hoping it works ok!

Thanks for all the hard work on this!

[maartenvanvliet]

For SCA this may also be needed #539

Feel free to cherry-pick that commit into this branch before merging.

[moomerman]

@snewcomer sorry was away last week so didn't get a chance to make v2.5.

I've addressed everything now, have left as separate commits for review but let me know if it's good and I'll squash them.

I wasn't sure about the last commit Add type for payment_method_options
d5c867b - whether this is necessary of just use a map.

[snewcomer]

What an amazing PR. Thank you thank you!

[snewcomer]

2.6 was released! Thank you @maartenvanvliet and @moomerman! Amazing work