public function registerMailTemplates(array $definitions)
    {
        if (!$this->registeredTemplates) {
            $this->registeredTemplates = [];
        }

        // Prior sytax where (key) code => (value) description
        if (!isset($definitions[0])) {
            $definitions = array_keys($definitions);
        }

        $definitions = array_combine($definitions, $definitions);

        $this->registeredTemplates = $definitions + $this->registeredTemplates;
    }