Enhance Form Submission Export Functionality (#657)

* Enhance Form Submission Export Functionality

* Validate new param 'columns'

* Form submission export request as seprate class with validation

* Test case for export

---------

Co-authored-by: Julien Nahum <julien@nahum.net>

api/app/Http/Requests/FormSubmissionExportRequest.php

@@ -0,0 +1,38 @@
+<?php
+
+namespace App\Http\Requests;
+
+use App\Models\Forms\Form;
+use Illuminate\Foundation\Http\FormRequest;
+use Illuminate\Http\Request;
+
+class FormSubmissionExportRequest extends FormRequest
+{
+    public Form $form;
+
+    public function __construct(Request $request)
+    {
+        $this->form = Form::findOrFail($request->route('id'));
+    }
+
+    public function rules()
+    {
+        $validColumns = collect(array_merge(
+            $this->form->properties,
+            $this->form->removed_properties ?? []
+        ))->pluck('id')->toArray();
+        $validColumns[] = 'created_at';
+
+        return [
+            'columns' => 'required|array',
+            'columns.*' => ['boolean', 'required'],
+            'columns' => [function ($attribute, $value, $fail) use ($validColumns) {
+                $submittedColumns = array_keys($value);
+                $invalidColumns = array_diff($submittedColumns, $validColumns);
+                if (!empty($invalidColumns)) {
+                    $fail('The columns contain invalid values: ' . implode(', ', $invalidColumns));
+                }
+            }],
+        ];
+    }
+}