Create datacube from UDP more easily

Currently, I need to create a datacube from a UDP as follows:

udp_sar = connection.save_user_defined_process(
    user_defined_process_id="s1_stats",
    process_graph=s1_stats,
    parameters=[temporal_extent, spatial_extent],
    summary="S1 SAR stats",
    description="Calculate S1 SAR stats (min, max, mean, sd, q10, q50, q90). This service can cost an approximate of 3-5 credits per sq km. This cost is based on resource consumpltion only and added-value cost has not been included.",
    public=True,
)
public_url, _ = [
    l["href"] for l in udp_sar.describe()["links"] if l["rel"] == "canonical"
]
sar = connection.datacube_from_process(
    "s1_stats",
    namespace=public_url,
    temporal_extent=["2023-05-01", "2023-07-30"],
    spatial_extent={"west": 8.82, "south": 44.40, "east": 8.92, "north": 44.45},
)

It would be nice if the client could allow to pass the UDP directly:

udp_sar = connection.save_user_defined_process(
    user_defined_process_id="s1_stats",
    process_graph=s1_stats,
    parameters=[temporal_extent, spatial_extent],
    summary="S1 SAR stats",
    description="Calculate S1 SAR stats (min, max, mean, sd, q10, q50, q90). This service can cost an approximate of 3-5 credits per sq km. This cost is based on resource consumpltion only and added-value cost has not been included.",
    public=True,
)
sar = connection.datacube_from_process(
    udp,
    temporal_extent=["2023-05-01", "2023-07-30"],
    spatial_extent={"west": 8.82, "south": 44.40, "east": 8.92, "north": 44.45},
)

Start by reading the connection.save_user_defined_process and connection.datacube_from_process entry points shown in the issue. Trace how the current process identifier and namespace are handled, then verify that datacube_from_process accepts the returned UDP directly while preserving the existing string-based form.