Cleanup SI Unit classes and interface for REST responses; fixes to a few METAR parsing issues

app/Http/Resources/Response.php

@@ -2,6 +2,7 @@
 
 namespace App\Http\Resources;
 
+use App\Interfaces\Unit;
 use Illuminate\Http\Resources\Json\Resource;
 
 /**
@@ -9,4 +10,22 @@ use Illuminate\Http\Resources\Json\Resource;
  */
 class Response extends Resource
 {
+    /**
+     * Iterate through the list of $fields and check if they're a "Unit"
+     * If they are, then add the response
+     *
+     * @param       $response
+     * @param array $fields
+     */
+    public function checkUnitFields(&$response, array $fields): void
+    {
+        foreach ($fields as $f) {
+            if ($this->{$f} instanceof Unit) {
+                $response[$f] = $this->{$f}->getResponseUnits();
+            } else {
+                $response[$f] = $this->{$f};
+            }
+        }
+    }
+
 }