ZIP Exports: Finished up format doc, move files, started builder

Moved all existing export related app files into their new own dir.

app/Exports/Controllers/ChapterExportController.php

@@ -0,0 +1,73 @@
+<?php
+
+namespace BookStack\Exports\Controllers;
+
+use BookStack\Entities\Queries\ChapterQueries;
+use BookStack\Exceptions\NotFoundException;
+use BookStack\Exports\ExportFormatter;
+use BookStack\Http\Controller;
+use Throwable;
+
+class ChapterExportController extends Controller
+{
+    public function __construct(
+        protected ChapterQueries $queries,
+        protected ExportFormatter $exportFormatter,
+    ) {
+        $this->middleware('can:content-export');
+    }
+
+    /**
+     * Exports a chapter to pdf.
+     *
+     * @throws NotFoundException
+     * @throws Throwable
+     */
+    public function pdf(string $bookSlug, string $chapterSlug)
+    {
+        $chapter = $this->queries->findVisibleBySlugsOrFail($bookSlug, $chapterSlug);
+        $pdfContent = $this->exportFormatter->chapterToPdf($chapter);
+
+        return $this->download()->directly($pdfContent, $chapterSlug . '.pdf');
+    }
+
+    /**
+     * Export a chapter to a self-contained HTML file.
+     *
+     * @throws NotFoundException
+     * @throws Throwable
+     */
+    public function html(string $bookSlug, string $chapterSlug)
+    {
+        $chapter = $this->queries->findVisibleBySlugsOrFail($bookSlug, $chapterSlug);
+        $containedHtml = $this->exportFormatter->chapterToContainedHtml($chapter);
+
+        return $this->download()->directly($containedHtml, $chapterSlug . '.html');
+    }
+
+    /**
+     * Export a chapter to a simple plaintext .txt file.
+     *
+     * @throws NotFoundException
+     */
+    public function plainText(string $bookSlug, string $chapterSlug)
+    {
+        $chapter = $this->queries->findVisibleBySlugsOrFail($bookSlug, $chapterSlug);
+        $chapterText = $this->exportFormatter->chapterToPlainText($chapter);
+
+        return $this->download()->directly($chapterText, $chapterSlug . '.txt');
+    }
+
+    /**
+     * Export a chapter to a simple markdown file.
+     *
+     * @throws NotFoundException
+     */
+    public function markdown(string $bookSlug, string $chapterSlug)
+    {
+        $chapter = $this->queries->findVisibleBySlugsOrFail($bookSlug, $chapterSlug);
+        $chapterText = $this->exportFormatter->chapterToMarkdown($chapter);
+
+        return $this->download()->directly($chapterText, $chapterSlug . '.md');
+    }
+}