fix: show ARP error samples in log message text instead of metadata

- Changed error logging to include sample errors directly in message string
- Ensures error details are visible regardless of logger metadata config
- Extracted format_error_samples/1 helper to reduce nesting (Credo)
- Helps diagnose ARP upsert failures in staging/production

lib/towerops/snmp.ex

@@ -1878,6 +1878,18 @@ defmodule Towerops.Snmp do
     end
   end
 
+  # Helper to format error samples into log message text
+  defp format_error_samples([]), do: ""
+
+  defp format_error_samples(samples) do
+    formatted_samples =
+      Enum.map_join(samples, "\n", fn sample ->
+        "  - IP: #{sample.ip}, MAC: #{sample.mac}, errors: #{inspect(sample.errors)}"
+      end)
+
+    "\nSample errors:\n" <> formatted_samples
+  end
+
   @doc """
   Bulk upserts ARP entries for a device.
   Returns `{success_count, error_count}` tuple.
@@ -1906,17 +1918,7 @@ defmodule Towerops.Snmp do
     end)
     |> tap(fn {_s, errors, error_samples} ->
       if errors > 0 do
-        samples_text =
-          case Enum.reverse(error_samples) do
-            [] ->
-              ""
-
-            samples ->
-              "\nSample errors:\n" <>
-                Enum.map_join(samples, "\n", fn sample ->
-                  "  - IP: #{sample.ip}, MAC: #{sample.mac}, errors: #{inspect(sample.errors)}"
-                end)
-          end
+        samples_text = error_samples |> Enum.reverse() |> format_error_samples()
 
         Logger.warning(
           "#{errors} ARP upsert failures for device #{device_id}#{samples_text}",