Added page export API controller

app/Http/Controllers/Api/PageExportApiController.php

@@ -0,0 +1,47 @@
+<?php namespace BookStack\Http\Controllers\Api;
+
+use BookStack\Entities\Models\Page;
+use BookStack\Entities\Tools\ExportFormatter;
+use Throwable;
+
+class PageExportApiController extends ApiController
+{
+    protected $exportFormatter;
+
+    public function __construct(ExportFormatter $exportFormatter)
+    {
+        $this->exportFormatter = $exportFormatter;
+    }
+
+    /**
+     * Export a page as a PDF file.
+     * @throws Throwable
+     */
+    public function exportPdf(int $id)
+    {
+        $page = Page::visible()->findOrFail($id);
+        $pdfContent = $this->exportFormatter->pageToPdf($page);
+        return $this->downloadResponse($pdfContent, $page->slug . '.pdf');
+    }
+
+    /**
+     * Export a page as a contained HTML file.
+     * @throws Throwable
+     */
+    public function exportHtml(int $id)
+    {
+        $page = Page::visible()->findOrFail($id);
+        $htmlContent = $this->exportFormatter->pageToContainedHtml($page);
+        return $this->downloadResponse($htmlContent, $page->slug . '.html');
+    }
+
+    /**
+     * Export a page as a plain text file.
+     */
+    public function exportPlainText(int $id)
+    {
+        $page = Page::visible()->findOrFail($id);
+        $textContent = $this->exportFormatter->pageToPlainText($page);
+        return $this->downloadResponse($textContent, $page->slug . '.txt');
+    }
+}