Remove various state.Model constructors

[mjs]

Description of change

This change makes most of the steps so that state.Model instances can only be created from state.State associated to that model. There were many ways to create a state.Model from any State which meant that the Model referred to a state.State associated with the wrong model. This is dangerous - requiring great care - and limits what can be done by Model instances.

Much functionality will soon be moved onto state.Model, requiring that the state.State it references is the correct one.

Change highlights:

• State.ControllerModel() has been replaced by State.ControllerModelTag() and State.ControllerModelUUID()
• State.AllModels() has been replaced by State.AllModelUUIDs()
• State.ModelsForUser() now returns UUIDs instead of UserModels. state.UserModel no longer exists.
• Fixed a bug in State.ModelsForUser() where dead or importing models could be reported for admin users.
• Access to Model instances is now done via state.State in most cases. Added a StatePool.GetModel() helper as a convenience.
• Many changes in the apiserver package resulted as fallout from the above. This resulted in most calls to State.ForModel() being removed (bug 1698702)

There is still one state.Model constructor to remove: state.State.GetModel(). This will be done in the next PR - this one was getting big enough.

QA steps

Confirmed that core model, controller and migration functionality worked:

$ juju bootstrap lxd source
# wait
$ juju bootstrap lxd target
# wait
$ juju switch source
$ juju add-model foo
$ juju deploy ubuntu
# wait
$ juju migrate foo target
# wait
$ juju debug-log -m source:controller -l ERROR # check controller logs for errors
$ juju debug-log -m target:controller -l ERROR # check controller logs for errors
$ juju destroy-controller -y --destroy-all-models source
$ juju destroy-controller -y --destroy-all-models target

Documentation changes

N.A. - internal only

Bug reference

Drive-by changes fixed https://bugs.launchpad.net/juju/+bug/1698702

[wallyworld]

Not sure i agree with this - the state shim is supposed to only wrap state to provide access to its methods.
I rather stick to keeping state and state pool separate in these shim objects to reflect the semantics of those structs

[mjs]

I had them separate initially but it worked out much nicer to wrap them together. The backend interface then just represents everything to do with "state". It make the tests cleaner too.

[wallyworld]

we have a state pool below, prefer to keep them seperate

[mjs]

I had missed that a pool was being used separately here. I would actually like to update the PR to extend the Backend interface to have a GetBackend method and not pass the pool directly to createOffersAPI at all.

Happy to discuss further of course.

[wallyworld]

as in GetBackend(uuid)? Like is done for model manager backend I'm guessing

[wallyworld]

It really returns the UUIDs right?
SHould these methods that still say "Models" be renamed to "ModelUUIDs" for better clarity?

[mjs]

Done

[wallyworld]

Please add a todo (or two) to alter the backends to just take a state pool

[mjs]

$$merge$$

[jujubot]

Status: merge request accepted. Url: http://juju-ci.vapour.ws:8080/job/github-merge-juju