API Changes for 8.x-2.x

#3055868: Delete entity load/delete wrappers

• simplenews_subscriber_load() => Subscriber::load()
• simplenews_subscriber_load_by_mail() => Subscriber::loadByMail()
• simplenews_subscriber_load_by_uid() => Subscriber::loadByUid()
• simplenews_subscriber_load_multiple() => Subscriber::loadMultiple()
• simplenews_subscriber_delete_multiple() => Use the entity storage's delete() method
• simplenews_newsletter_load() => Newsletter::load()
• simplenews_newsletter_load_multiple() => Newsletter::loadMultiple()

#3052727: Create clear consolidated functions to send/cancel newsletters

• SpoolStorage::addFromEntity(), simplenews_issue_update_sent_status() => SpoolStorage::addIssue()
• SpoolStorage::deleteMails('nid') => SpoolStorage::deleteIssue()

#3053650: Subscriber counts ignore RecipientHandlerInterface::count()

• simplenews_count_subscriptions() => SpoolStorage::issueCountRecipients()

#3055769: Mail spool inconsistent between nodes / entities

• MailInterface::getEntity() => MailInterface::getIssue()

#1931006: Problem with recipient handlers

• simplenews_get_recipient_handler() => SpoolStorage::getRecipientHandler()
• Significant changes to RecipientHandlerInterface and configuration passed to recipient handler.
• Old class RecipientHandlerBase => RecipientHandlerAll (and there is a new RecipientHandlerBase)

#3062530: Fix and simplify subscriber creation/lookup/sync

• SubscriberInterface::isSyncing(), SubscriberInterface::setSyncing(), SubscriberInterface::setUserId(), SubscriberInterface::getUserSharedFields() all deleted from public interface
• Callers should use SubscriberInterface::fillFromAccount() and SubscriberInterface::copyToAccount(), and the details of syncing are handled internally.

#3052714: Send failures retried forever

• SpoolListInterface::getProcessed() => SpoolListInterface::setLastMailResult() called after each mail then SpoolListInterface::getResults() called once at end.
• Status of sending is represented by a simple integer, one of the SpoolStorageInterface::STATUS_* constants instead of the array with two keys bool and int used previously. Affects: MailerInterface::sendMail(), SpoolStorageInterface::updateMails(), SpoolListInterface::getResults().