Add ingress, catalogue relations to terraform modules

[sed-i]

We need to have mimir, tempo listed on the catalogue page.

Depends on:

• Add catalogue relation mimir-coordinator-k8s-operator#97
• Add catalogue relation tempo-coordinator-k8s-operator#87
• Add catalogue relation cos-lib#113

This would involve adding ingress relations to mimir, tempo, as they are currently missing from the terraform module.
This may be a bit involved: after manually relating mimir to traefik, I am getting a 404 from nginx for all mimir endpoints.

References:

• https://github.com/canonical/cos-lite-bundle/blob/907103f88b0e00d2bd83eadcd6d7b01ef8260aea/bundle.yaml.j2#L62
• Add catalogue + ingress tempo integrations in COS TF module #253

[sed-i]

This could have been happening because the /status path is already used by an nginx endpoint mapping.
We shouldn't shadow known workload paths with our custom ones.
The trouble is that /status may be a hard dep for the nginx exporter.

[simskij]

Why do we want to have tempo? It has no UI. Mimir potentially makes sense, but I'd honestly skip it. I'm sure I've asked for this at some point, but I think we can skip this.

[lucabello]

@simskij @sed-i canonical/tempo-coordinator-k8s-operator#93 added some form of that for Tempo. Mimir has the same one, while Loki has a "simpler" UI not for the generic memberlist, but for the distributor ring:

Another alternative, as we discussed in a separate meeting, is to add an empty link, explaining the lack of UI in the catalogue item description.

How do we want to do this?

[lucabello]

We're gonna go for the empty links for now, for both Mimir and Loki, and eventually change it in the future!