Add load/dump state

lib/vaccins/location_store.ex

@@ -88,8 +88,7 @@ defmodule Vaccins.LocationStore do
 
   @impl true
   def init(_opts) do
-    locations = read_file() |> Map.new(&{&1.id, &1})
-    {:ok, %{locations: locations}}
+    {:ok, load_state()}
   end
 
   def get_locations() do
@@ -124,9 +123,10 @@ defmodule Vaccins.LocationStore do
              }
              |> Location.set_id(),
            locations <- locations |> Map.put(processed.id, processed),
-           :ok <- locations |> Map.values() |> write_file() do
+           new_state <- %{locations: locations},
+           :ok <- new_state |> dump_state do
         :ok
-        {:reply, :ok, %{locations: locations}}
+        {:reply, :ok, new_state}
       else
         e = {:error, _} -> {:reply, e, state}
       end
@@ -135,10 +135,13 @@ defmodule Vaccins.LocationStore do
   @impl true
   def handle_call({:delete_location, id}, _, state = %{locations: locations}) do
     with locations <- locations |> Map.delete(id),
-         :ok <- locations |> Map.values() |> write_file(),
-         do: {:reply, :ok, %{locations: locations}}
+         new_state <- %{locations: locations},
+         :ok <- new_state |> dump_state,
+         do: {:reply, :ok, new_state}
   end
 
+  defp load_state(), do: %{locations: read_file() |> Map.new(&{&1.id, &1})}
+
   defp read_file(),
     do:
       with(
@@ -147,6 +150,8 @@ defmodule Vaccins.LocationStore do
         do: decoded |> Enum.map(&Location.from_json/1)
       )
 
+  defp dump_state(state = %{locations: locations}), do: locations |> Map.values() |> write_file()
+
   defp write_file(locations),
     do:
       with(