Can't add two clusters with the same name

Currently we cross-reference clusters by their name, so having two or more clusters with the same name causes serious problems.

Possible solutions:

• Use UUID instead
  • Not user-friendly (Grafana doesn't let us have e.g. a variable that displays the name but actually evaluates to the UUID, and having users select clusters by UUID is a non-starter)
  • The only way we could make this work is by hiding the Cluster variable on all dashboards and relying on inter-linking from the Inventory to set it correctly - this would solve the problem, though it isn't great from a UX perspective as it'd mean you have to go back to the inventory to switch clusters
• Use aliases
  • Cluster Monitor would need to be modified to output aliases to its Prometheus metrics as labels
    • Would this cause issues for clusters that don't have aliases? Need to check
  • We'd need to modify the add cluster flow to add the alias as a secondary label
  • Possibly could be done alongside CMOS-187 (hierarchy + metadata for clusters)
• Disallow it completely
  • The easiest solution, but certainly not viable long-term
  • If we did this we'd need the config service to check what clusters are already registered with Prometheus and refuse to add one with the same name