MDL-70983 badges: Remove OBv1.0 support

The only backpack implementing OBv1.0 was Mozilla Backpack. It closed
in 2019 and their badges were moved to https://backpack.openbadges.org/
by Badgr.
However, as Badgr is supporting OBv2.0 too, it makes no sense keep OBv1.0
implementation in Moodle: it has caused some issues and over-complicates
current code.

badges/classes/backpack_api_mapping.php

@@ -31,10 +31,6 @@ global $CFG;
 require_once($CFG->libdir . '/filelib.php');
 
 use context_system;
-use core_badges\external\assertion_exporter;
-use core_badges\external\collection_exporter;
-use core_badges\external\issuer_exporter;
-use core_badges\external\badgeclass_exporter;
 use curl;
 
 /**
@@ -82,7 +78,7 @@ class backpack_api_mapping {
     /** @var mixed List of parameters for this method. */
     protected $postparams;
 
-    /** @var int OpenBadges version 1 or 2. */
+    /** @var int OpenBadges version. */
     protected $backpackapiversion;
 
     /**
@@ -98,7 +94,7 @@ class backpack_api_mapping {
      * @param boolean $json json decode the response.
      * @param boolean $authrequired Authentication is required for this request.
      * @param boolean $isuserbackpack user backpack or a site backpack.
-     * @param integer $backpackapiversion OpenBadges version 1 or 2.
+     * @param integer $backpackapiversion OpenBadges version.
      */
     public function __construct($action, $url, $postparams, $requestexporter, $responseexporter,
                                 $multiple, $method, $json, $authrequired, $isuserbackpack, $backpackapiversion) {
@@ -233,32 +229,6 @@ class backpack_api_mapping {
         return $request;
     }
 
-    /**
-     * Read the response from a V1 user request and save the userID.
-     *
-     * @param string $response The request response.
-     * @param integer $backpackid The backpack id.
-     * @return mixed
-     */
-    private function convert_email_response($response, $backpackid) {
-        global $SESSION;
-
-        if (isset($response->status) && $response->status == 'okay') {
-
-            // Remember the tokens.
-            $useridkey = $this->get_token_key(BADGE_USER_ID_TOKEN);
-            $backpackidkey = $this->get_token_key(BADGE_BACKPACK_ID_TOKEN);
-
-            $SESSION->$useridkey = $response->userId;
-            $SESSION->$backpackidkey = $backpackid;
-            return $response->userId;
-        }
-        if (!empty($response->error)) {
-            self::set_authentication_error($response->error);
-        }
-        return false;
-    }
-
     /**
      * Get the user id from a previous user request.
      *