This would allow to script which retrieves the last swhid of an object [1] by composing
multiple calls from the client [2]
[1] T3192#69844
[2]
```
from swh.web.client.client import WebAPIClient
client = WebAPIClient()
url = "https://doi.org/10.5201/ipol.2018.236"
visit = client.last_visit(url)
# if visit...
snapshot = next(client.snapshot(visit["snapshot"]))
# if snapshot ...
revision = client.revision(snapshot['HEAD']['target'])
# ensure target_type == 'revision'
# if revision
In [17]: str(revision['directory'])
Out[17]: 'swh:1:dir:d85591aeefea2c1c58142e34683fd1923b19c895'
```
Related to T3192