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

Call full status 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.

internal/juju/applications.go

@@ -901,12 +901,12 @@ func (c applicationsClient) ReadApplication(input *ReadApplicationInput) (*ReadA
 
 	appInfo := apps[0].Result
 
-	// We are currently retrieving the full status, which might be more information than necessary.
-	// The main focus is on the application status, particularly including the storage status.
-	// It might be more efficient to directly query for the application status and its associated storage status.
-	// TODO: Investigate if there's a way to optimize this by only fetching the required information.
+	// Fetch data only about the application being read. This helps to limit
+	// the data on storage to the specific application too. Storage is not
+	// provided by application, rather storage data buries a unit name deep
+	// in the structure.
 	status, err := clientAPIClient.Status(&apiclient.StatusArgs{
-		Patterns:       []string{},
+		Patterns:       []string{input.AppName},
 		IncludeStorage: true,
 	})
 	if err != nil {

internal/provider/resource_application_test.go

@@ -41,6 +41,7 @@ func TestAcc_ResourceApplication(t *testing.T) {
 					resource.TestCheckResourceAttr("juju_application.this", "charm.0.name", "jameinel-ubuntu-lite"),
 					resource.TestCheckResourceAttr("juju_application.this", "trust", "true"),
 					resource.TestCheckResourceAttr("juju_application.this", "expose.#", "1"),
+					resource.TestCheckNoResourceAttr("juju_application.this", "storage"),
 				),
 			},
 			{