docs(pulp): add step to perform image data migration

The command `pulpcore-manager container-handle-image-data`[0] can be used
to resolve issues with missing image fields.

[0]: pulp/pulp_container#1554

Author: jackhodgkiss

doc/source/operations/upgrading-openstack.rst

@@ -153,20 +153,8 @@ Known issues
 Pulp Upgrade
 ------------
 
-It was found that if pulp is upgraded from 3.43.1 to 3.81.0, most of pulp
-APIs become unusable because of a bug related to missing response header
-when docker clients expect it.
-
-Generally pulp is considered to be safe to completely destroy and re-deploy.
-So, users are encouraged to upgrade pulp in this method.
-
-If your pulp has custom built images, we recommended either not doing pulp
-upgrade by pinning pulp version at ``seed_pulp_container.pulp.tag`` in
-``$KAYOBE_CONFIG_PATH/seed.yml`` (``$KAYOBE_CONFIG_PATH/environments/<env>/seed.yml``
-if using environments) to 3.43.1,
-
-or pulling all custom built images before destroying pulp then push them again
-after pulp upgrade is done.
+After Pulp has been upgraded it is important to run ``pulpcore-manager container-handle-image-data``
+otherwise attempts to pull images will fail with ```Error response from daemon: missing or empty Content-Length header``.
 
 Cinder
 ------
@@ -896,6 +884,10 @@ To upgrade the containerised seed services:
 
 .. code-block:: console
 
+   kayobe seed service deploy --tags seed-deploy-containers --kolla-tags none
+   ssh stack@<seed>
+   sudo docker exec pulp pulpcore-manager container-handle-image-data
+   exit
    kayobe seed service upgrade
 
 Verify that Bifrost, Ironic and Inspector are running as expected: