Prometheus Targets configured via CMR are not named usefully

[Drew Freiberger]

When deploying prometheus2 charm into a separate model from the telegraf charm, for instance, the name of the exporter endpoint type is "remote-$UUID" instead of "telegraf". This makes investigating prometheus target endpoints tedious as you need to know the port numbers for each exporter (telegraf, p-ceph-exporter, p-openstack-exporter, p-libvirt-exporter, etc).

It would be very useful to get the proper remote application name through the CMR relation to exporters.

To reproduce, create two models, lma and workload, offer the

juju add-model workload
juju deploy cs:ubuntu
juju deploy cs:telegraf
juju offer telegraf:prometheus-client

juju add-model lma
juju deploy cs:prometheus2
juju add-relation prometheus2:target admin/workload.telegraf

juju status prometheus2 # to get the service IP and port
visit the prometheus2 endpoint and click on Status->Targets and observe that the telegraf client endpoints have a header of "remote-$some_uuid (1/1 up)". It would be helpful if this showed something like "workload.telegraf" or "$workload_model_uuid.telegraf".