[ADD] project/milestones: using project milestones

closes odoo/documentation#15258

Task-id: 3305827
Signed-off-by: Xavier Platteau (xpl) <xpl@odoo.com>

content/applications/services/project/project_management.rst

@@ -156,4 +156,6 @@ You can also create your own buttons to access more specific views:
 
    project_management/project_dashboard
    project_management/project_profitability
+   project_management/project_milestones
    project_management/project_templates
+

content/applications/services/project/project_management/project_dashboard.rst

@@ -67,8 +67,8 @@ The following smart buttons are displayed on the top right of the project dashbo
 Milestones
 ----------
 
-This section is only visible if :doc:`milestones </applications/sales/sales/invoicing/milestone>`
-have been enabled in the project you're browsing: go to :guilabel:`Project`, click the
+This section is only visible if :doc:`milestones <../project_management/project_milestones>` have
+been enabled in the project you're browsing: go to :guilabel:`Project`, click the
 :icon:`fa-ellipsis-v` (:guilabel:`vertical ellipsis`) icon on one of your projects, and click on
 :guilabel:`Settings`. Click on the :guilabel:`Settings` tab, look for :guilabel:`Tasks Management`
 and make sure :guilabel:`Milestones` is enabled.

content/applications/services/project/project_management/project_milestones.rst

@@ -0,0 +1,67 @@
+==================
+Project milestones
+==================
+
+**Milestones** enable you to track ongoing project work by designating a sequence of key steps that
+must be reached before the project’s completion. Milestones are particularly useful in expensive,
+long, or large-scale projects. They can be used purely for indicative purposes, as a way to ensure
+that the project is completed in a timely manner.
+
+Milestones can also be used as a basis for :doc:`invoicing the client </applications/sales/sales/invoicing/milestone>`.
+This benefits both parties, as it ensures consistent cash flow for project funding and allows the
+client to pay for the project in several installments.
+
+Configuration
+=============
+
+Enable milestones for the desired project by opening the :guilabel:`Project` app, clicking the
+:icon:`fa-ellipsis-v` (:guilabel:`vertical ellipsis`) on the project’s card, and clicking
+:guilabel:`Settings`. Under :guilabel:`Tasks Management`, enable :guilabel:`Milestones`.
+
+.. note::
+   Milestones are automatically enabled for projects created from a sales order for a service
+   :doc:`invoiced by milestone </applications/sales/sales/invoicing/milestone>`.
+
+Configure project milestones by clicking the :icon:`fa-ellipsis-v` (:guilabel:`vertical ellipsis`)
+on the project’s card and selecting :guilabel:`Milestones`. Create a milestone by clicking
+:guilabel:`New`, entering the milestone's :guilabel:`Name`, selecting a :guilabel:`Deadline` if
+desired, and clicking :guilabel:`Save`.
+
+Add or remove options by clicking the :icon:`oi-settings-adjust` :guilabel:`sliders`. The following
+options are relevant when using
+:doc:`invoicing based on milestones </applications/sales/sales/invoicing/milestone>`:
+
+ - :guilabel:`Sales Order Item`: this field is filled in automatically with the Sales Order number.
+ - :guilabel:`Quantity (%)`: percentage of the ordered quantity that will automatically be delivered
+   on the sales order once the milestone is marked as reached.
+
+Once milestones are configured, **you can link project tasks to milestones**. To do so, navigate to
+the project you created the milestones in, then click one of the tasks to open it. Then, click the
+:guilabel:`Milestone` field to open a drop-down menu. Select the desired milestone from the list.
+
+Once all the tasks linked to the milestone are completed (marked as
+:doc:`Done or Cancelled <../tasks/task_stages_statuses>`), the milestone will be automatically
+marked as :guilabel:`Reached` in the :menuselection:`Project --> Settings --> Milestones`. You can
+also check the :guilabel:`Reached` box manually whenever the milestone is reached. Manual checking
+of the box will not impact the tasks linked to the milestone.
+
+Using milestones
+================
+
+Odoo offers several ways to oversee the project’s milestones and their relationship to ongoing
+tasks.
+
+In the **Gantt view**, a milestone is shown as a vertical line marked with a diamond shape,
+displayed on the day of the milestone’s deadline. The line is color-coded in blue to indicate that
+the milestone has not yet reached its deadline, or it has been marked as reached (in which case, a
+check mark is displayed on the milestone). A milestone is color-coded in red if it has not been
+reached by its deadline.
+
+If a milestone’s deadline falls on the same day as the project’s deadline, it is displayed with a
+vertical line marked with a circle, and the same color coding principles as above apply.
+
+Aside from the Gantt view, you can also create, edit, and mark milestones as reached from
+:ref:`the project dashboard <project/project-dashboard/milestones>`.
+
+.. image:: project_milestones/gantt-milestones.png
+   :alt: Project milestones in Gantt view.