Clicking on a cluster populates the Dashboard URL search bar with an unexpected URL

**What happened**:

Pressing the cluster in the dask-labextension panel on the left side of JupyterLab 3 provided me with a unknown URL that doesn't seem to relate to the dashboard URL of the cluster in any way.



**My wish**

I wish that the same Dashboard URL declared for the cluster is populating the search bar when I press the cluster.

I see three variations that could happen when I press the cluster.

1. `dask/dashboard/ee31a59b-71a8-4464-86c8-7cc8df558497` --- I find this strange, where did this come from? This is the current behavior
2. `/services/dask-gateway/clusters/prod.f9abd4530de44f958847aed333400ff2/status` --- This is what I expected, but this doesn't work as it doesn't know about the domain name etc.
3. `https://hub.jupytearth.org/services/dask-gateway/clusters/prod.f9abd4530de44f958847aed333400ff2/status` --- This is what I'd truley want, but think may be out of scope for this issue.

**Minimal Complete Verifiable Example**:

I don't know how to provide this =/

**Environment**:

JupyterHub (1.1.1 Helm chart) + Dask-Gateway (0.9.0 Helm chart).

```
$ conda list | grep dask
dask 2021.6.0 pyhd8ed1ab_0 conda-forge
dask-core 2021.6.0 pyhd8ed1ab_0 conda-forge
dask-gateway 0.9.0 py38h578d9bd_0 conda-forge
dask-glm 0.2.0 py_1 conda-forge
dask-kubernetes 2021.3.1 pyhd8ed1ab_0 conda-forge
dask-labextension 5.0.2 pyhd8ed1ab_0 conda-forge
dask-ml 1.9.0 pyhd8ed1ab_0 conda-forge
pangeo-dask 2021.06.05 hd8ed1ab_0 conda-forge
```

```
$ python --version
Python 3.8.10
```

Operating System: Ubuntu 20.04
Install method: conda-forge

```
# The current environment and dask configuration via environment
DASK_DISTRIBUTED__DASHBOARD_LINK=/user/{JUPYTERHUB_USER}/proxy/{port}/status
DASK_GATEWAY__ADDRESS=http://10.100.116.39:8000/services/dask-gateway/
DASK_GATEWAY__AUTH__TYPE=jupyterhub
DASK_GATEWAY__CLUSTER__OPTIONS__IMAGE={JUPYTER_IMAGE_SPEC}
DASK_GATEWAY__PROXY_ADDRESS=gateway://traefik-prod-dask-gateway.prod:80
DASK_GATEWAY__PUBLIC_ADDRESS=/services/dask-gateway/
DASK_LABEXTENSION__FACTORY__CLASS=GatewayCluster
DASK_LABEXTENSION__FACTORY__MODULE=dask_gateway
DASK_ROOT_CONFIG=/srv/conda/etc
```