Before this commit, the rainbow man message at the end of tours is fixed to a hardcoded message. This commit allows to customize the message within the definition of the tour, to add the ability to use tailored messages depending on the app the tour is about. If no custom message is set, the old default will still be used. Task ID: 2241549 closes odoo/odoo#49779 Signed-off-by: Yannick Tivisse (yti) <yti@odoo.com>