The same user (reader) can also create/update volume metadata as well as update/delete volume metadata item.

create volume metadata:
2023-07-30 09:08:48,418 91159 INFO     [tempest.lib.common.rest_client] Request (ProjectReaderTests:test_create_volume_metadata): 200 POST https://158.69.72.48/volume/v3/34fdf801453342b98866f178838a72ea/volumes/a12cf7d1-3aa4-4ecd-a514-e8f3fe39cbd7/metadata 0.246s
2023-07-30 09:08:48,419 91159 DEBUG    [tempest.lib.common.rest_client] Request - Headers: {'Content-Type': 'application/json', 'Accept': 'application/json', 'Openstack-Api-Version': 'volume 3.12', 'X-Auth-Token': '<omitted>'}
        Body: {"metadata": {"key1": "value1", "key2": "value2", "key3": "value3", "key4": "value4"}}
    Response - Headers: {'date': 'Sun, 30 Jul 2023 09:08:48 GMT', 'server': 'Apache/2.4.52 (Ubuntu)', 'content-type': 'application/json', 'x-compute-request-id': 'req-16346c48-74c9-4721-aa4d-8b42453574d4', 'content-length': '86', 'openstack-api-version': 'volume 3.12', 'vary': 'OpenStack-API-Version', 'x-openstack-request-id': 'req-16346c48-74c9-4721-aa4d-8b42453574d4', 'connection': 'close', 'status': '200', 'content-location': 'https://158.69.72.48/volume/v3/34fdf801453342b98866f178838a72ea/volumes/a12cf7d1-3aa4-4ecd-a514-e8f3fe39cbd7/metadata'}
        Body: b'{"metadata": {"key1": "value1", "key2": "value2", "key3": "value3", "key4": "value4"}}'


update volume metadata:
2023-07-30 09:09:16,833 91159 INFO     [tempest.lib.common.rest_client] Request (ProjectReaderTests:test_update_volume_metadata): 200 POST https://158.69.72.48/volume/v3/34fdf801453342b98866f178838a72ea/volumes/b9aaa4d5-1ef5-4619-94c2-cd3b16d5b831/metadata 0.050s
2023-07-30 09:09:16,834 91159 DEBUG    [tempest.lib.common.rest_client] Request - Headers: {'Content-Type': 'application/json', 'Accept': 'application/json', 'Openstack-Api-Version': 'volume 3.12', 'X-Auth-Token': '<omitted>'}
        Body: {"metadata": {"key1": "value1", "key2": "value2", "key3": "value3", "key4": "value4"}}
    Response - Headers: {'date': 'Sun, 30 Jul 2023 09:09:16 GMT', 'server': 'Apache/2.4.52 (Ubuntu)', 'content-type': 'application/json', 'x-compute-request-id': 'req-a1d5854d-b19f-4a41-9091-958da50a9792', 'content-length': '86', 'openstack-api-version': 'volume 3.12', 'vary': 'OpenStack-API-Version', 'x-openstack-request-id': 'req-a1d5854d-b19f-4a41-9091-958da50a9792', 'connection': 'close', 'status': '200', 'content-location': 'https://158.69.72.48/volume/v3/34fdf801453342b98866f178838a72ea/volumes/b9aaa4d5-1ef5-4619-94c2-cd3b16d5b831/metadata'}
        Body: b'{"metadata": {"key1": "value1", "key2": "value2", "key3": "value3", "key4": "value4"}}'


update volume metadata item:
2023-07-30 09:09:20,355 91159 INFO     [tempest.lib.common.rest_client] Request (ProjectReaderTests:test_update_volume_metadata_item): 200 PUT https://158.69.72.48/volume/v3/34fdf801453342b98866f178838a72ea/volumes/776bd91b-b857-45a1-80ad-b9f1559fb692/metadata/key2 0.036s
2023-07-30 09:09:20,356 91159 DEBUG    [tempest.lib.common.rest_client] Request - Headers: {'Content-Type': 'application/json', 'Accept': 'application/json', 'Openstack-Api-Version': 'volume 3.12', 'X-Auth-Token': '<omitted>'}
        Body: {"meta": {"key2": "value2_updated"}}
    Response - Headers: {'date': 'Sun, 30 Jul 2023 09:09:20 GMT', 'server': 'Apache/2.4.52 (Ubuntu)', 'content-type': 'application/json', 'x-compute-request-id': 'req-ba453fe4-c19f-4776-aeac-02d7bc51a600', 'content-length': '36', 'openstack-api-version': 'volume 3.12', 'vary': 'OpenStack-API-Version', 'x-openstack-request-id': 'req-ba453fe4-c19f-4776-aeac-02d7bc51a600', 'connection': 'close', 'status': '200', 'content-location': 'https://158.69.72.48/volume/v3/34fdf801453342b98866f178838a72ea/volumes/776bd91b-b857-45a1-80ad-b9f1559fb692/metadata/key2'}
        Body: b'{"meta": {"key2": "value2_updated"}}'



delete volume metadata item
2023-07-30 09:08:52,067 91159 INFO     [tempest.lib.common.rest_client] Request (ProjectReaderTests:test_delete_volume_metadata_item): 200 DELETE https://158.69.72.48/volume/v3/34fdf801453342b98866f178838a72ea/volumes/4137f68b-71e4-4fb0-aa04-d06bbc76dc5f/metadata/key1 0.046s
2023-07-30 09:08:52,067 91159 DEBUG    [tempest.lib.common.rest_client] Request - Headers: {'Content-Type': 'application/json', 'Accept': 'application/json', 'Openstack-Api-Version': 'volume 3.12', 'X-Auth-Token': '<omitted>'}
        Body: None
    Response - Headers: {'date': 'Sun, 30 Jul 2023 09:08:52 GMT', 'server': 'Apache/2.4.52 (Ubuntu)', 'content-length': '0', 'content-type': 'text/html; charset=UTF-8', 'openstack-api-version': 'volume 3.12', 'vary': 'OpenStack-API-Version,Accept-Encoding', 'x-openstack-request-id': 'req-32d62e50-269b-4c94-a695-8ef0c9d33db7', 'connection': 'close', 'status': '200', 'content-location': 'https://158.69.72.48/volume/v3/34fdf801453342b98866f178838a72ea/volumes/4137f68b-71e4-4fb0-aa04-d06bbc76dc5f/metadata/key1'}
        Body: b''