chore: Comment Mercury logic

lib/screens/v2/screen_data.ex

@@ -23,6 +23,8 @@ defmodule Screens.V2.ScreenData do
           data: serializable_map() | nil,
           force_reload: boolean(),
           disabled: boolean(),
+          # Mercury uses this to help optimize data refreshes
+          # https://app.asana.com/0/1185117109217413/1205234924224431/f
           last_deploy_timestamp: DateTime.t()
         }
   @type paging_metadata :: %{

lib/screens/v2/widget_instance/departures.ex

@@ -405,6 +405,8 @@ defmodule Screens.V2.WidgetInstance.Departures do
           serialize_timestamp(departure_time, now)
       end
 
+    # time_in_epoch is used by Mercury so they can calculate timestamps on their own.
+    # https://app.asana.com/0/1176097567827729/1205730972991228/f
     %{time: time, time_in_epoch: DateTime.to_unix(departure_time)}
   end
 

lib/screens/v2/widget_instance/line_map.ex

@@ -239,6 +239,8 @@ defmodule Screens.V2.WidgetInstance.LineMap do
       if index < 0 do
         []
       else
+        # time_in_epoch is used by Mercury so they can calculate times on their own.
+        # https://app.asana.com/0/1176097567827729/1205730972991228/f
         departure_time_epoch = d |> Departure.time() |> DateTime.to_unix()
         [%{id: vehicle_id, index: index, label: label, time_in_epoch: departure_time_epoch}]
       end

lib/screens/v2/widget_instance/normal_header.ex

@@ -18,6 +18,8 @@ defmodule Screens.V2.WidgetInstance.NormalHeader do
           time: DateTime.t()
         }
 
+  # Mercury adds their own time so we omit the time in the response.
+  # https://app.asana.com/0/1185117109217413/1206070378353406/f
   def serialize(
         %__MODULE__{
           screen: %Screen{vendor: :mercury, app_id: :gl_eink_v2},

lib/screens_web/controllers/v2/screen_controller.ex

@@ -152,6 +152,8 @@ defmodule ScreensWeb.V2.ScreenController do
 
   # Handles widget page GET requests with widget data as a query param.
   # Phoenix does not automatically decode JSON received in query params.
+  # Primarily used by Mercury so not all requests need to run through the framework.
+  # https://app.asana.com/0/1185117109217413/1205234924224431/f
   def widget(conn, %{"app_id" => app_id, "widget" => json_data}) when is_binary(json_data) do
     case Jason.decode(json_data) do
       {:ok, widget_data} ->