[IMP] Event and website event evolution

Event access

• Created new group "Gestion des sessions & séances"
• Access right for this group have been set up so only members from this group can CRUD event sessions
• Access right for all other users (out side of the group) have been downgraded to only read access of event and event sessions
• Session related fields have been set invisible and a new button has apperead to turn enable/disable event session type
• Replaced flake8 and black with Ruff in the pre-commit file

Event and website event management

• Handle several website event with the same name where views could collide due to odoo menus URL definition
• Added copy of event with its sessions
• Added cascade delete of website event along with its views and menus
• Added event id in the view key string for better usage and singularity