feat: support firmware uploads, OTA pushes

lib/localiser/domain/sensors.ex

@@ -59,6 +59,27 @@ defmodule Localiser.Domain.Sensors do
     {:ok, sensor}
   end
 
+  def send_ota_update(%Sensor{} = sensor, url, version) do
+    payload = %{
+      action: "ota",
+      url: url,
+      version: version
+    }
+
+    Localiser.MQTT.Connection.publish(cmd_topic(sensor), Jason.encode!(payload))
+    {:ok, sensor}
+  end
+
+  def send_ota_broadcast(url, version) do
+    payload = %{
+      action: "ota",
+      url: url,
+      version: version
+    }
+
+    Localiser.MQTT.Connection.publish("localiser/ota", Jason.encode!(payload))
+  end
+
   # Pushes new WiFi and/or MQTT broker settings to the sensor. The sensor will
   # apply the changes and restart. All keys are optional — omit any you don't
   # want to change. Valid keys: "ssid", "password", "mqtt_host", "mqtt_port".