Support the [Online Access] and [Offline Access] oauth types

[nozzlegear]

Shopify has announced a new type of access token that you can receive during the OAuth signup flow. For support, this lib will need to add a grants string array property when building an authorization URL. The only known value is per-user.

Leaving the grants array blank will return an access token that's identical to the one that was given before this change, though Shopify now calls this an "offline access" token. Specifying per-user in the grants array will give you the new "online access" token.

This page goes into the difference between the two tokens, but to summarize: the new "online access" token is like a temporary user password to the store. It's guaranteed to respect the user's permissions with the store, and it will expire after the user logs out of their Shopify account.

[nozzlegear]

Closed with release 2.1.0.