Purpose fo the task is to improve the usability of hr contract and
automatic alert before contract expired
-improve sign demo data
-improve kanban state field in contract kanban
-improve contract Form view ui
-set first contract date on employee form
-added the date of last completed contract on the new contract
-improve signature request form
-create automatic activity before the week of contract expired date
closes odoo/odoo#40789
Task: 2049413
Closes: #40789
Related: odoo/enterprise#7454
Signed-off-by: Yannick Tivisse (yti) <yti@odoo.com>