[schema] Modify device token to support both iOS and Android

This replaces the AppleDeviceToken table with a generic
PushDeviceToken with a `kind` field to make it easier to add functionality
like per-device/per-stream settings that share code between Android and
iOS devices.

The schema must continue to work on prod with the old table name, so we
add the new table in parallel and can drop the old table once this code
hits prod and any necessary data is copied.

(imported from commit 0209a7013f2850ac6311f23c3d6f92c65ffd19e3)

zerver/lib/actions.py

@@ -6,7 +6,7 @@ from django.contrib.sessions.models import Session
 from zerver.lib.context_managers import lockfile
 from zerver.models import Realm, RealmEmoji, Stream, UserProfile, UserActivity, \
     Subscription, Recipient, Message, UserMessage, valid_stream_name, \
-    DefaultStream, UserPresence, Referral, MAX_SUBJECT_LENGTH, \
+    DefaultStream, UserPresence, Referral, PushDeviceToken, MAX_SUBJECT_LENGTH, \
     MAX_MESSAGE_LENGTH, get_client, get_stream, get_recipient, get_huddle, \
     get_user_profile_by_id, PreregistrationUser, get_display_recipient, \
     to_dict_cache_key, get_realm, stringify_message_dict, bulk_get_recipients, \