Supported cross-track upgrade paths

[MichaelThamm]

We agreed that we should guarantee upgrade paths from previous non-LTS to the current track and from previous tracks to their latest LTS track. This is not documented anywhere in the stack documentation. This might be a good place for it:

• https://documentation.ubuntu.com/observability/latest/release-notes/
• https://documentation.ubuntu.com/observability/latest/reference/release-policy/

Regardless of using TF or Juju CLI for cross-track upgrades, we should start to show maturity in this space by documenting it.

[MichaelThamm]

This is not something we do not need today because we want the upgrade path from track/1 to track/2 then to track/3 instead of supporting track/1 to track/3 (LTS). In the future we do want this.

Tip

It will take a few cycles until this will actually be useful to feature in docs.