feat: add jaas validators

[kian99]

Description

This PR adds two new validators related to JAAS.

1. AvoidJAASValidator in validator_avoid_jaas.go - This validator can be used to ensure a resource is not used with JAAS. E.g. juju_access_model should not be used with JAAS as there is a JAAS specific type for that.
2. RequiresJAASValidator in validator_require_jaas.go - This validator can be used to ensure a resource is only used with JAAS. For example, new JAAS specific resources should not be used when communicating with a regular Juju controller.

The output error messages require input from a technical author.

Type of change

• Other: Adds new validator.

Additional notes

https://warthogs.atlassian.net/browse/CSS-9768

[alesstimec]

suggestion

if v.Client != nil && v.Client.IsJAAS() {

[hmlanigan]

Please add more details on why in the commit messages and other places. Be kind to reviewer and your future self. It's not clear at all why we need both a AvoidJAAS and RequireJAAS validator. Some details are in the PR, but that is a long way to travel for the details.

[hmlanigan]

issue: a not nil client will hopefully be caught before this point, however please follow the known pattern along the lines of:

	// Check first if the client is configured
	if a.client == nil {
		addClientNotConfiguredError(&resp.Diagnostics, "access model", "create")
		return
	}

For both validators

[kian99]

I don't think we should do that here, the validator is called multiple times throughout the process of resource creation, it is expected that the client will be nil at certain stages before the client has been created.
I'll leave a comment to that effect.

[hmlanigan]

The client I'm thinking of is created as part of the jujuProvider.Config method at the very start. It's created before any resource schema is known. This block of code is recommended by terraform framework tutorials.

I'm unclear why you believe the client may be nil during resource creation?

The check is more of a paranoia check as the client should be available.

[kian99]

I added the nil check because when I was investigating when the validator is called you will find that it is executed multiple times, including before the resource' configure method is called.

Only when the resource's configure method is called, is the resource's client populated (by using the client created in jujuProvider.Config) and no longer nil.

The easiest way to see this is to run one of the integration tests in debug mode and step through the code. There you can see that the client will be nil at certain points and if we were to return an error because the client was not yet configured the resource would always fail to be created because this value is always nil before the configure method is called.

[hmlanigan]

suggestion: This resource can only be used with JAAS, which offers additional enterprise features - see https://jaas.ai/ for more details.

[kian99]

Can you also please assign @tmihoc for review as there was a request for a technical author to look over these error messages.

[hmlanigan]

I have doubts these validators will work, as I'm not sure a not nil client can be provided to them. When I did some test runs with code myself and never found a case where the client was not nil when calling a validator as set up here which surprised me.

We're in a feature branch, so let's move forward. They will have to be validated once code is available to use them.

@tmihoc hasn't provided feedback on the wording yet. Changes can be made later.

[tmihoc]

Some nitpicks and a clarification question about the error message.

[tmihoc]

The sentence about JAAS is jarring because it shifts the topic from resources (the previous two sentences) to JAAS, and the connection to resources is unclear -- i.e., as a user, what I'm getting is that dedicated resources can help me take advantage of the additional enterprise features of JAAS, but it's not clear to me what "dedicated resources" is referring to and what I'm supposed to do with this information (i.e., am I suppose to not use the resource suggested in the hint?)

[kian99]

I see what you mean. What if we changed this sentence to,

"JAAS offers additional enterprise features through the use of dedicated resources (those with "jaas" in the name)."

The hint is created above and supposed to lead the user to the correct resource to use - it will say something like "Try the juju_jaas_access_model resource instead."