fix: bugs 535 and 539 only find storage for application being read

[hmlanigan]

Description

FullStatus was called without a filter. The storage returned in the structure was assumed to be for the application being read. In reality it was for all application's in the model. Unfortunately piecing which storage is for which application is non-trivial as the data is embedded deep in the structure on a unit level.

Instead call FullStatus with a filter of the application name when Reading, this ensures that the returned storage is for the current application only.

Updated an application acceptance test to ensure storage isn't written for applications without storage.

Fixes: #535, #539, #550

Type of change

• Bug fix (non-breaking change which fixes an issue)

QA steps

terraform {
  required_providers {
    juju = {
      version = ">0.12.0"
      source  = "juju/juju"
    }
  }
}

provider "juju" {
}

resource "juju_model" "one" {
  name = "testing"
}

resource "juju_application" "test" {
   model = juju_model.one.name
   charm {
     name = "juju-qa-test"
   }
}

resource "juju_application" "githubrunner" {
  name  = "github-runner"
  model = juju_model.one.name

  charm {
    name     = "github-runner"
    channel  = "latest/stable"
    base = "[email protected]"
  }
  units = 1

  storage_directives = {
    runner = "2G"
  }
}

# output from the below should include storage_directive and storage
$ terraform state show juju_application.githubrunner

# output from below should not include any mention of storage
$ terraform state show juju_application.test

Additional notes

JUJU-6599

[Aflynn50]

Excellent! I tried out the reproducer from bug #550 and it seems that issue is fixed too!
Just left a comment about the comment above the line changed.

[hmlanigan]

/merge