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- apns: Add new APNS configuration value ``APNS_DEFAULT_BATCH_SIZE`` and set to ``100``.
- apns: Add ``batch_size`` parameter to APNS ``send`` that can be used to override ``APNS_DEFAULT_BATCH_SIZE``.
- apns: Make APNS ``send`` batch multiple notifications into a single payload. Previously, individual socket writes were performed for each token. Now, socket writes are batched based on either the ``APNS_DEFAULT_BATCH_SIZE`` configuration value or the ``batch_size`` function argument value.
- apns: Make APNS ``send`` resume sending from after the failed token when an error response is received.
- apns: Make APNS ``send`` raise an ``APNSSendError`` when one or more error responses received. ``APNSSendError`` contains an aggregation of errors, all tokens attempted, failed tokens, and successful tokens. (**breaking change**)
- apns: Replace ``priority`` argument to APNS ``send`` with ``low_priority=False``. (**breaking change**)