[IMP] rma: finish RMA manually

Sometimes there's no choice to return, refund or replace an RMA for
different reasons. For example, when the customer doesn't want to repair
the product because that would be too expensive. We still want finish
the RMA and document the reasons. This improvement allows it.

TT34164

rma/README.rst

@@ -51,6 +51,11 @@ If you want RMAs to be created from incoming emails, you need to:
    one.
 #. Go to 'Email' tab and set an 'Email Alias'.
 
+If you want to manually finish RMAs, you need to:
+
+#. Go to *Settings > Inventory*.
+#. Set *Finish RMAs manually* checkbox on.
+
 Usage
 =====
 
@@ -79,6 +84,11 @@ To use this module, you need to:
      The RMA will be set automatically to 'Replaced' or 'Returned' state when
      the RMA quantity is equal or lower than the quantity in done delivery
      orders linked to it.
+#. You can also finish the RMA without further ado. To do so click on the *Finish*
+   button. A wizard will ask you for the reason from a selection of preconfigured ones.
+   Be sure to configure them in advance on *RMA > Configuration > Finalization Reasons*.
+   Once the RMA is finished, it will be set to that state and the reason will be
+   registered.
 
 An RMA can also be created from a return of a delivery order: