[Community] Enhanced team and role management

[WolfyWin]

Q	A
Bug fix?	no
New feature?	yes
BC breaks?	no

Added an option when creating a team to choose whether or not to use existing roles.

• Added of a Boolean field on the Team entity to store whether or not existing roles are used.
• Removal "delete cascade" on the role and managerRole relationships of Team entity.
• Removal of the uniqueness constraint on the Team entity for role_id and manager_role_id.
• New field added to serializer and deserializer.
• Add new 'useExistingRoles' field in the form.
• Prevent roles from being created automatically when the team is created if useExistingRoles = true.
• Prevent team roles from being deleted when the team is deleted if they are existing roles.