Fix flight page errors and some naming fixes

app/Models/Traits/ExpensableTrait.php

@@ -0,0 +1,27 @@
+<?php
+
+namespace App\Models\Traits;
+
+use App\Models\Expense;
+
+trait ExpensableTrait
+{
+    public static function bootExpensable()
+    {
+
+    }
+
+    /**
+     * Morph to Expenses.
+     * @return mixed
+     */
+    public function expenses()
+    {
+        return $this->morphMany(
+            Expense::class,
+            'expenses',  # overridden by the next two anyway
+            'ref_class',
+            'ref_class_id'
+        );
+    }
+}