Handle type casting for longinteger inputs

Implemented `cast_value/2` functions to support string input parsing for `:longinteger` values and arrays in server-owned interfaces.

Signed-off-by: Ismet Softic <ismet.softic@secomind.com>

CHANGELOG.md

@@ -52,6 +52,9 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
   where database_retention_ttl exceeds the realm's maximum datastream storage
   retention period, if set.
 
+### Fixed
+- [astarte_appengine_api] Handle type casting for `longinteger` inputs
+
 ## [1.1.2] - Unreleased
 ### Added
 - [astarte_data_updater_plant] customize the number of consumer connections

apps/astarte_appengine_api/lib/astarte_appengine_api/device/device.ex

@@ -775,6 +775,29 @@ defmodule Astarte.AppEngine.API.Device do
     end
   end
 
+  defp cast_value(:longinteger, string_value) when is_binary(string_value) do
+    with {int_value, _} <- Integer.parse(string_value) do
+      {:ok, int_value}
+    else
+      :error ->
+        {:error, :unexpected_value_type, expected: :longinteger}
+    end
+  end
+
+  defp cast_value(:longinteger, _string_value) do
+    {:error, :unexpected_value_type, expected: :longinteger}
+  end
+
+  defp cast_value(:longintegerarray, string_values) do
+    case map_while_ok(string_values, &cast_value(:longinteger, &1)) do
+      {:ok, mapped_values} ->
+        {:ok, mapped_values}
+
+      _ ->
+        {:error, :unexpected_value_type, expected: :longintegerarray}
+    end
+  end
+
   defp cast_value(_anytype, anyvalue) do
     {:ok, anyvalue}
   end