Add rel note and example for TOKEN_DELETE_DISABLED

https://review.openstack.org/#/c/340689 added a new setting to Django
OpenStack Auth. This patch documents it and provides an example.

Change-Id: Ib684b4c918af0d5ae3770cba702b44e86a3ad3da
Closes-Bug: 1609506

doc/source/topics/settings.rst

@@ -1111,6 +1111,16 @@ Example::
 .. note::
   The value is expected to be a tuple formatted as: (<idp_id>, <protocol_id>).
 
+``TOKEN_DELETE_DISABLED``
+-------------------------
+
+.. versionadded:: 10.0.0(Newton)
+
+Default: ``False``
+
+This setting allows deployers to control whether a token is deleted on log out.
+This can be helpful when there are often long running processes being run
+in the Horizon environment.
 
 ``OPENSTACK_CINDER_FEATURES``
 -----------------------------

openstack_dashboard/local/local_settings.py.example

@@ -222,6 +222,11 @@ OPENSTACK_KEYSTONE_BACKEND = {
 # allowing Admin session password retrieval/decryption.
 #OPENSTACK_ENABLE_PASSWORD_RETRIEVE = False
 
+# This setting allows deployers to control whether a token is deleted on log
+# out. This can be helpful when there are often long running processes being
+# run in the Horizon environment.
+#TOKEN_DELETE_DISABLED = False
+
 # The Launch Instance user experience has been significantly enhanced.
 # You can choose whether to enable the new launch instance experience,
 # the legacy experience, or both. The legacy experience will be removed

releasenotes/notes/token-delete-disabled-bb50c3cddd315ee6.yaml

@@ -0,0 +1,4 @@
+---
+features:
+  - Added the ``TOKEN_DELETE_DISABLED`` setting, so that deployers can
+    customise the revocation of a users token on log out.