Django-shopify-auth

Changed
- Fix issue where `next` parameter wasn't honored when `SHOPIFY_APP_THIRD_PARTY_COOKIE_CHECK` is enabled.
Added
- Added a middleware to accommodate changes to SameSite policy.

Changed
- 3rd party cookie check is now disabled by default as it doesn't pass Shopify's review check.
- Increased the token field max_length
- Updated test matrix to test only supported Django and Python versions

Added
- Added a mixin which verifies that the current shop is authenticated and app is installed in shopify.
Removed
- Dropped support for Django 1.x

Added
- Detection if third party cookies are allowed

Removed
- Dropped support for Python 3.4

Added
- Support for Django 3 by removing Python 2 support

Removed
- Dropped support for Python 2

Added
- Support for `return_to` redirect parameter.
- Added Django v2.1, v2.2 and v2.3 to test matrix.

Removed
- Support for deprecated Django versions 1.x.

Changed
- Added support for Shopify API versioning.