v2.0

Important updates

• Breaking change: Drop support for deprecated WEBHOOK_AUTHORIZATION setting. If you are using webhooks and still have this Anymail setting, you must rename it to WEBHOOK_SECRET. See the v1.4 release notes.

New features

• SendinBlue: Add new ESP (docs). Thanks to @RignonNoel for the implementation.
• Add EmailMessage envelope_sender attribute, which can adjust the message's Return-Path if supported by your ESP (docs).
• Add universal wheel to PyPI releases for faster installation.

Other changes

• Handle Reply-To, From, and To in EmailMessage extra_headers the same as Django's SMTP EmailBackend if supported by your ESP, otherwise raise an unsupported feature error. Fixes the SparkPost backend to be consistent with other backends if both headers["Reply-To"] and reply_to are set on the same message. If you are setting a message's headers["From"] or headers["To"] (neither is common), the new behavior is likely a breaking change. See docs and #91.
• Treat EmailMessage extra_headers keys as case-insensitive in all backends, for consistency with each other (and email specs). If you are specifying duplicate headers whose names differ only in case, this may be a breaking change. See docs.
• Update setup.py metadata, clean up implementation. (Hadn't really been touched since original Djrill version.)
• Prep for Python 3.7.