[ADD] slides gallery module

- Task: https://www.odoo.com/web?#id=9093&view_type=form&model=project.task
- Pad: https://pad.odoo.com/p/r.QlQTvBv6mCcMrK4B
goal of this method is unclear (and method name is too generic to be clear)
return types mismatch (this method sometimes returns a string, sometimes a boolean... I bet this works only by accident!

=> can you explain what you're trying to do and refactor your code?