Add abstract class for route finding mechanism

app/Contracts/RouteFinder.php

@@ -0,0 +1,24 @@
+<?php
+
+namespace App\Contracts;
+
+/**
+ * Abstract class for finding a route from a departure airport to an arrival airport
+ * Can allow for multiple, configurable methods for finding a route, whether it reaches
+ * out to a REST API or implement some sort of internal logic to look through a file
+ * or whatever the logic might be.
+ *
+ * Just one public-facing method needs to be implemented
+ */
+abstract class RouteFinder
+{
+    /**
+     * Find a route from the departure ICAO to the arrival ICAO
+     *
+     * @param $dptIcao
+     * @param $arrIcao
+     *
+     * @return string
+     */
+    abstract public function findRoute($dptIcao, $arrIcao): string;
+}