Stack trace
INSERT INTO xf_user (`visible`, `activity_visible`, `user_group_id`, `timezone`, `language_id`, `username`, `email`, `user_state`, `display_style_group_id`, `secondary_group_ids`, `secret_key`, `user_id`, `style_id`, `permission_combination_id`, `message_count`, `alerts_unread`, `conversations_unread`, `register_date`, `last_activity`, `trophy_points`, `avatar_date`, `avatar_width`, `avatar_height`, `avatar_highdpi`, `gravatar`, `is_moderator`, `is_admin`, `is_staff`, `is_banned`, `like_count`, `custom_title`, `warning_points`) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
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#0 src/XF/Db/Mysqli/Statement.php(174): XF\Db\AbstractStatement->getException('MySQL query err...', 1062, '23000')
#1 src/XF/Db/Mysqli/Statement.php(69): XF\Db\Mysqli\Statement->getException('MySQL query err...', 1062, '23000')
#2 src/XF/Db/AbstractAdapter.php(69): XF\Db\Mysqli\Statement->execute()
#3 src/XF/Db/AbstractAdapter.php(144): XF\Db\AbstractAdapter->query('INSERT INTO xf...', Array)
#4 src/XF/Mvc/Entity/Entity.php(1343): XF\Db\AbstractAdapter->insert('xf_user', Array)
#5 src/XF/Mvc/Entity/Entity.php(1085): XF\Mvc\Entity\Entity->_saveToSource()
#6 src/XF/Service/User/Registration.php(254): XF\Mvc\Entity\Entity->save()
#7 src/XF/Service/ValidateAndSavableTrait.php(40): XF\Service\User\Registration->_save()
#8 src/XF/Pub/Controller/Register.php(367): XF\Service\User\Registration->save()
#9 src/XF/Mvc/Dispatcher.php(249): XF\Pub\Controller\Register->actionRegister(Object(XF\Mvc\ParameterBag))
#10 src/XF/Mvc/Dispatcher.php(87): XF\Mvc\Dispatcher->dispatchClass('XF:Register', 'Register', 'json', Object(XF\Mvc\ParameterBag), '', Object(XF\Pub\Controller\Register), NULL)
#11 src/XF/Mvc/Dispatcher.php(41): XF\Mvc\Dispatcher->dispatchLoop(Object(XF\Mvc\RouteMatch))
#12 src/XF/App.php(1844): XF\Mvc\Dispatcher->run()
#13 src/XF.php(328): XF\App->run()
#14 index.php(13): XF::runApp('XF\\Pub\\App')
#15 {main}