Invalidate stored service password if the endpoint URL is changed
This MR handles bugs (introduced by !1558 (merged)):
- It is not possible to set a new URL and a password at the same time (new password is ignored)
- An error occurs on the Service Templates admin pages (prop_updated? was referencing the service's project, which is not defined for templates)
- Passwords are reset on every save in Service Templates admin pages
Related !1583 (merged)