MDL-59645 repository_flickr: Drop legacy auth tokens and nsids

The values stored in these user preferences were valid for the old
flickr auth mechanism and are not usable any more. The new oauth1 based
version needs to store both the token (in the flickr_access_token
preference) and the token secret (flickr_access_token_secret). The new
version does not need to store the user's nsid.

The cryptic names of these legacy settings are a result of how dealing
with user preferences was originally implemented.

repository/flickr/db/upgrade.php

@@ -0,0 +1,48 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Plugin upgrade steps are defined here.
+ *
+ * @package     repository_flickr
+ * @category    upgrade
+ * @copyright   2017 David Mudrák <[email protected]>
+ * @license     http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+defined('MOODLE_INTERNAL') || die();
+
+/**
+ * Execute repository_flickr upgrade from the given old version.
+ *
+ * @param int $oldversion
+ * @return bool
+ */
+function xmldb_repository_flickr_upgrade($oldversion) {
+    global $DB;
+
+    $dbman = $DB->get_manager();
+
+    if ($oldversion < 2017082200) {
+        // Drop legacy flickr auth tokens and nsid's.
+        $DB->delete_records('user_preferences', ['name' => 'flickr_']);
+        $DB->delete_records('user_preferences', ['name' => 'flickr__nsid']);
+
+        upgrade_plugin_savepoint(true, 2017082200, 'repository', 'flickr');
+    }
+
+    return true;
+}

repository/flickr/version.php

@@ -26,6 +26,6 @@
 
 defined('MOODLE_INTERNAL') || die();
 
-$plugin->version   = 2017051500;        // The current plugin version (Date: YYYYMMDDXX)
+$plugin->version   = 2017082200;        // The current plugin version (Date: YYYYMMDDXX)
 $plugin->requires  = 2017050500;        // Requires this Moodle version
 $plugin->component = 'repository_flickr'; // Full name of the plugin (used for diagnostics)