This commit improves the structure of the Subscription doc and updates
its content (recurring products, subscription plans, sales flow)
task-3222232
closesodoo/documentation#4062
Signed-off-by: Castillo Jonathan (jcs) <jcs@odoo.com>
Co-authored-by: Xavier Platteau <xpl@odoo.com>
Co-authored-by: Tom Aarab <toaa@odoo.com>"