Add no search engine index plugin see BT#13757 - requires composer update

- Hide portal from search engines bots editing the robots.txt file and
adding a meta tag "noindex".

plugin/nosearchindex/README.md

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+No search index
+===
+
+This plugin allows administrators to hide the portal from search engines using the robots.txt file and adding a meta tag "noindex".

plugin/nosearchindex/index.php

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+<?php

plugin/nosearchindex/install.php

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+<?php

plugin/nosearchindex/lang/english.php

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+<?php
+
+$strings['plugin_title'] = "No search engine index";
+$strings['plugin_comment'] = "Hide portal from search engine bots.";
+$strings['tool_enable'] = 'Enable plugin';

plugin/nosearchindex/plugin.php

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+<?php
+/* For licensing terms, see /license.txt */
+
+/**
+ * @package chamilo.plugin
+ */
+
+/** @var \NoSearchIndex $plugin */
+$plugin = NoSearchIndex::create();
+$plugin_info = $plugin->get_info();
+
+$isPlatformAdmin = api_is_platform_admin();
+$editFile = false;
+
+$file = api_get_path(SYS_PATH).'robots.txt';
+
+if ($isPlatformAdmin) {
+    $originalFile = api_get_path(SYS_PATH).'robots.dist.txt';
+    if (!file_exists($originalFile)) {
+        copy($file, $originalFile);
+    }
+
+    $originalContent = file_get_contents($originalFile);
+
+    $form = $plugin_info['settings_form'];
+
+    if ($form->validate()) {
+        $values = $form->getSubmitValues();
+        $contents = file_get_contents($originalFile);
+        $extraContentFile = api_get_home_path().'header_extra_content.txt';
+        $noFollow = '<meta name="robots" content="noindex" />';
+
+        if (isset($values['tool_enable']) && $values['tool_enable'] == 'true') {
+            file_put_contents($file, $contents."\nDisallow: /\n");
+            $value = '';
+            if (file_exists($extraContentFile)) {
+                $backup = file_get_contents($extraContentFile);
+                file_put_contents($extraContentFile, $backup.$noFollow);
+            } else {
+                $value = file_put_contents($extraContentFile, $noFollow);
+            }
+        } else {
+            file_put_contents($file, $contents);
+
+            if (file_exists($extraContentFile)) {
+                $backup = file_get_contents($extraContentFile);
+                $backup = str_replace($noFollow, '', $backup);
+                file_put_contents($extraContentFile, $backup);
+            }
+        }
+    }
+    $plugin_info['settings_form'] = $form;
+}
+