Add support for passing line item information to offsite integrations.

[ntalbott]

Issue by melari
Wednesday Oct 30, 2013 at 14:10 GMT
Originally opened as https://github.com/Shopify/active_merchant/pull/894

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This defines a standard way to pass line item information to integrations. Individual integrations can then override the line_item method to suit their needs.

There are already a few integrations which support passing in line items such as auth.net sims. These should be refactored to this common interface as some point.

@odorcicd @RichardBlair

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melari included the following code: https://github.com/Shopify/active_merchant/pull/894/commits