zilencer: Add new model RemoteRealm and send the data to the bouncer.

Add the new model for recording basic information about Realms on remote
server, to go with the other analytics data. Also adds necessary changes
to the bouncer endpoint and the send_analytics_to_push_bouncer()
function to submit such Realm information.

zilencer/models.py

@@ -84,6 +84,41 @@ class RemotePushDeviceToken(AbstractPushDeviceToken):
         return f"{self.server!r} {self.user_id}"
 
 
+class RemoteRealm(models.Model):
+    """
+    Each object corresponds to a single remote Realm that is using the
+    Mobile Push Notifications Service via `manage.py register_server`.
+    """
+
+    server = models.ForeignKey(RemoteZulipServer, on_delete=models.CASCADE)
+
+    # The unique UUID and secret for this realm.
+    uuid = models.UUIDField(unique=True)
+    uuid_owner_secret = models.TextField()
+
+    # Value obtained's from the remote server's realm.host.
+    host = models.TextField()
+
+    # The fields below are analogical to RemoteZulipServer fields.
+
+    last_updated = models.DateTimeField("last updated", auto_now=True)
+
+    # Whether the realm registration has been deactivated.
+    registration_deactivated = models.BooleanField(default=False)
+    # Whether the realm has been deactivated on the remote server.
+    realm_deactivated = models.BooleanField(default=False)
+
+    # When the realm was created on the remote server.
+    realm_date_created = models.DateTimeField()
+
+    # Plan types for self-hosted customers
+    PLAN_TYPE_SELF_HOSTED = 1
+    PLAN_TYPE_STANDARD = 102
+
+    # The current billing plan for the remote server, similar to Realm.plan_type.
+    plan_type = models.PositiveSmallIntegerField(default=PLAN_TYPE_SELF_HOSTED, db_index=True)
+
+
 class RemoteZulipServerAuditLog(AbstractRealmAuditLog):
     """Audit data associated with a remote Zulip server (not specific to a
     realm).  Used primarily for tracking registration and billing