`juju changes` to show history of changes for a model?

Hi,

Would it be possible to add an option to show the list of changes to a specific model? Changes being when application change has been upgraded, when unit has been added or removed, etc.?

Similar to `snap changes`:

| $ snap changes
| ID Status Spawn Ready Summary
| 452 Done today at 10:10 UTC today at 10:11 UTC Auto-refresh snap "google-cloud-cli"
| 453 Done today at 17:10 UTC today at 17:11 UTC Auto-refresh snap "google-cloud-cli"

I think a list of things I would like to see would be:

 * when model was upgraded to specific version of Juju.

 * when application was deployed.

 * when charm has been upgraded from which version to which version. etc.

 * when unit X was added or removed.

 * when changes were applied / updated to a specific application.

Would be useful for model operators to audit and see what change happened when.