Added usage graph (ADSL), improved logging for usage collection (ADSL)

app/Interfaces/ServiceUsage.php

@@ -0,0 +1,16 @@
+<?php
+
+namespace App\Interfaces;
+
+use Illuminate\Support\Collection;
+
+interface ServiceUsage
+{
+	/**
+	 * This service provides usage information
+	 *
+	 * @param int $days
+	 * @return Collection
+	 */
+	public function usage(int $days): Collection;
+}