Draft: [IMP] Acces rights & Ruff

• 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

data/group_session.xml

+<?xml version="1.0" encoding="utf-8" ?>
+<odoo>
+    <record id="group_event_session" model="res.groups">
+      <field name="name">Gestion des sessions et séances</field>
+    </record>
+</odoo>