[App] Actually fix launching apps on multiple clusters

[luca3rd]

What does this PR do?

Actually fix the cross launching apps issue.

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Fixes #<issue_number>

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[lantiga]

I don't think this is what we want.

App names must be unique per-project, not per-project + per-cluster @edenafek (I feel strongly about this).

If you try to run an app with the same name in a project, targeting a different cluster, the first app needs to be stopped, irrespective of what cluster it is running on. We need to keep the model simple, otherwise the CLI will complicate a ton (now it's not enough to address the app by name, you also need to think whether there's another instance of that app running on another cluster, and instead use the id to address it, e.g. connect, from the CLI).

[rusenask]

I don't think this is what we want.

App names must be unique per-project, not per-project + per-cluster @edenafek (I feel strongly about this).

If you try to run an app with the same name in a project, targeting a different cluster, the first app needs to be stopped, irrespective of what cluster it is running on. We need to keep the model simple, otherwise the CLI will complicate a ton (now it's not enough to address the app by name, you also need to think whether there's another instance of that app running on another cluster, and instead use the id to address it, e.g. connect, from the CLI).

👍 I also don't think this is useful for any scenario. Why would you have the same name @edenafek ? If I wanted this as a user I would just create two apps muse-east-1 and muse-east-2 and then I don't have to think about it. This is almost as having two files in your directory with the same name, while possible, doesn't make things good :)

[lantiga]

Requested change (throughout the system): app names should be unique per project

[dmitsf]

Suggested change

	existing_instance = existing_instances_by_cluster.get(app_config.cluster_id, None)
	existing_instance = existing_instances_by_cluster.get(app_config.cluster_id)

[dmitsf]

None is already the default returning value :)

[luca3rd]

This was an old PR to prove that we could launch app instances on different clusters.

The PR fixing this issue as we discussed is over here: #15484