Fixes (#435)

* Add flight level field to PIREP field closes #401

* Default value for distance 0 closes #400

* Block airline deletion if assets exist #367

* Formatting

* Move some of the base exception classes

* Fix skin references to use settings table

* Set default for theme name if setting is wrong

app/Exceptions/AbstractHttpException.php

@@ -0,0 +1,62 @@
+<?php
+
+namespace App\Exceptions;
+
+use Symfony\Component\HttpKernel\Exception\HttpException as SymfonyHttpException;
+use Symfony\Component\HttpKernel\Exception\HttpExceptionInterface;
+
+/**
+ * Abstract class for an exception which needs to satisty the RFC 78707 interface
+ */
+abstract class AbstractHttpException extends SymfonyHttpException implements HttpExceptionInterface
+{
+    /**
+     * Return the RFC 7807 error type (without the URL root)
+     */
+    abstract public function getErrorType(): string;
+
+    /**
+     * Get the detailed error string
+     */
+    abstract public function getErrorDetails(): string;
+
+    /**
+     * Return an array with the error details, merged with the RFC7807 response
+     */
+    abstract public function getErrorMetadata(): array;
+
+    /**
+     * Return the error message as JSON
+     */
+    public function getJson()
+    {
+        $response = [];
+
+        $response['type'] = config('phpvms.error_root').'/'.$this->getErrorType();
+        $response['title'] = $this->getMessage();
+        $response['details'] = $this->getErrorDetails();
+        $response['status'] = $this->getStatusCode();
+
+        // For backwards compatibility
+        $response['error'] = [
+            'status'  => $this->getStatusCode(),
+            'message' => $this->getErrorDetails(),
+        ];
+
+        return array_merge($response, $this->getErrorMetadata());
+    }
+
+    /**
+     * Return a response object that can be used by Laravel
+     *
+     * @return \Illuminate\Http\JsonResponse|\Illuminate\Http\Response
+     */
+    public function getResponse()
+    {
+        $headers = [];
+        $headers['content-type'] = 'application/problem+json';
+        $headers = array_merge($headers, $this->getHeaders());
+
+        return response()->json($this->getJson(), $this->getStatusCode(), $headers);
+    }
+}