refactor(members): remove leader_of methods from member model/controller
feat(membership): add MembershipsController + update ServicesController#update method
feat(endpoints): add new CRUD endpoints for task and services
feat(endpoints): update Member et Service controller

- Members#Update: add possibilty to update a member without updating its services
- Service#Update: add member_in_charge_in to the attribute list updated on update
feat(leadership): try to assign the first member of a service as a leader when the actuel leader leaves
Merge branch 'release/0.9'