[DOC] Share server migration

[Carlos Eduardo]

Description
-----------

Update the manila documentation to fit into change: https://review.opendev.org/#/c/747043/ which was merged during the Victoria cycle.

Add share server migration

This patch adds support for migration of share servers. This
migration is performed using a two-phase approach. Administrators
are now able to request the migration of a share server within and
across backends, with the possibility of chooosing a different share
network for the destination share server.

- A new field called `task_state` was added to the share server
  model in order to help the administrator to track the share server
  migration steps. A new field called `source_share_server_id` was
  added to link destination and source share servers.

- A new periodic task was added to track migration of share servers
  and its resources.

- Two new states were added: `server_migrating` and
  `server_migrating_to` to represent that share migration is in
  progress.

- When performing the server migration, manila will not go to the
  scheduler, instead it will provide a request spec to drivers
  during migration check driver call. It'll be up to the driver
  validate if there is free space to handle the share server.

- A new API called `share-server-migration-check' was added to
  check the feasibility of a migration, before actually triggering
  the start operation.

APIImpact
DocImpact
Partially Implements: bp share-server-migration

Co-Authored-By: Andre Beltrami <email address hidden>
Co-Authored-By: Carlos Eduardo <email address hidden>
Co-Authored-By: Felipe Rodrigues <email address hidden>

Change-Id: Ic0751027d2c3f1ef7ab0f7836baff3070a230cfd
Signed-off-by: Douglas Viroel <email address hidden>

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/756144

[OpenStack Infra (hudson-openstack)]

Related fix proposed to branch: master
Review: https://review.opendev.org/756145

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/756297

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/756145
Committed: https://git.openstack.org/cgit/openstack/manila/commit/?id=3ca9c7678e4d1277a0cbe2dc967d5f2990d25d2b
Submitter: Zuul
Branch: master

commit 3ca9c7678e4d1277a0cbe2dc967d5f2990d25d2b
Author: Douglas Viroel <email address hidden>
Date: Wed Sep 30 13:54:14 2020 +0000

    Add share server migration admin documentation

    Partial-Bug: #1897903
    Change-Id: Ia6dd260e6d2f9e2a7d9d381d345d952a3069f8c5
    Signed-off-by: Douglas Viroel <email address hidden>

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/victoria
Review: https://review.opendev.org/758099

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/758099
Committed: https://git.openstack.org/cgit/openstack/manila/commit/?id=9de17f66b7cc4967e15e9782304026ef5f0ca821
Submitter: Zuul
Branch: stable/victoria

commit 9de17f66b7cc4967e15e9782304026ef5f0ca821
Author: Douglas Viroel <email address hidden>
Date: Wed Sep 30 13:54:14 2020 +0000

    Add share server migration admin documentation

    Partial-Bug: #1897903
    Change-Id: Ia6dd260e6d2f9e2a7d9d381d345d952a3069f8c5
    Signed-off-by: Douglas Viroel <email address hidden>
    (cherry picked from commit 3ca9c7678e4d1277a0cbe2dc967d5f2990d25d2b)