[ActivityPub] Autofix profile URIs through alias discovering

Activitypub_profile:
- Add updateUri method

explorer:
- Add grab_aliases method
- Update grab_local_user's online course to grab and test aliases

plugins/ActivityPub/classes/Activitypub_profile.php

@@ -495,6 +495,21 @@ class Activitypub_profile extends Managed_DataObject
         return $profile;
     }
 
+    /**
+     * Update remote user profile URI in local instance
+     *
+     * @param string $uri
+     * @return void
+     * @throws Exception (if the update fails)
+     * @author Bruno Casteleiro <brunoccast@fc.up.pt>
+     */
+    public function updateUri(string $uri)
+    {
+        $orig = clone($this);
+        $this->uri = $uri;
+        $this->updateWithKeys($orig);
+    }
+
     /**
      * Getter for the number of subscribers of a
      * given local profile