The initial cinder design[1][2][3] allowed users to create mutliattach volumes by spcifying the ``multiattach`` parameter in the request body of volume create operation (``--allow-multiattach`` option in cinderclient). This functionality changed in Queens with the introduction of microversion 3.50[4] where we used volume types to store the multiattach capabilities. Any volume created with a multiattach volume type will be a multiattach volume[5]. While implementing the new functionality, we had to keep backward compatibility with the *old way* of creating multiattach volumes. We deprecated the ``multiattach`` (``--allow-multiattach`` on cinderclient side) parameter in the queens release[6][7]. We also removed the support of the ``--allow-multiattach`` optional parameter from cinderclient in the train release[8] but the API side never removed the compatibility code to disallow functionality of creating multiattach volumes by using the ``multiattach`` parameter (instead of a multiattach volume type). This patch removes the support of providing the ``multiattach`` parameter in the request body of a volume create operation and will fail with a BadRequest exception stating the reason of failure and how it can be fixed. [1] https://blueprints.launchpad.net/cinder/+spec/multi-attach-volume [2] https://review.opendev.org/c/openstack/cinder/+/85847/ [3] https://review.opendev.org/c/openstack/python-cinderclient/+/85856 [4] https://github.com/openstack/cinder/commit/f1bfd9790d2a7cac9a3e66417b11dc8e3edd8109 [5] https://docs.openstack.org/cinder/latest/admin/volume-multiattach.html#how-to-create-a-multiattach-volume [6] https://github.com/openstack/cinder/commit/94dbf5cce2caff484460a1330feb6cbf7f3dd56a [7] https://github.com/openstack/python-cinderclient/commit/adb141a2626192e8f45a911291895716d7c1c8a4 [8] https://github.com/openstack/python-cinderclient/commit/3c1b417959689c85a2f54505057ca995fedca075 Depends-On: https://review.opendev.org/c/openstack/tempest/+/875372 Closes-Bug: 2008259 Change-Id: I0ece6e279048abcc04b3674108290a80eca6bd62