GC: Restore: Mail: Create Subfolder Feature (#1055)

## Description
The feature allows for the subFolders to be created. Test Suite Expanded. 
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## Type of change

<!--- Please check the type of change your PR introduces: --->
- [x] 🌻 Feature
## Issue(s)

<!-- Can reference multiple issues. Use one of the following "magic words" - "closes, fixes" to auto-close the Github issue. -->
*Closes Issue #1054<issue>

## Test Plan

- [x] ⚡ Unit test

src/internal/connector/exchange/service_functions.go

@@ -68,15 +68,31 @@ func createService(credentials account.M365Config, shouldFailFast bool) (*exchan
 // CreateMailFolder makes a mail folder iff a folder of the same name does not exist
 // Reference: https://docs.microsoft.com/en-us/graph/api/user-post-mailfolders?view=graph-rest-1.0&tabs=http
 func CreateMailFolder(ctx context.Context, gs graph.Service, user, folder string) (models.MailFolderable, error) {
+	isHidden := false
 	requestBody := models.NewMailFolder()
 	requestBody.SetDisplayName(&folder)
-
-	isHidden := false
 	requestBody.SetIsHidden(&isHidden)
 
 	return gs.Client().UsersById(user).MailFolders().Post(ctx, requestBody, nil)
 }
 
+func CreateMailFolderWithParent(
+	ctx context.Context,
+	gs graph.Service,
+	user, folder, parentID string,
+) (models.MailFolderable, error) {
+	isHidden := false
+	requestBody := models.NewMailFolder()
+	requestBody.SetDisplayName(&folder)
+	requestBody.SetIsHidden(&isHidden)
+
+	return gs.Client().
+		UsersById(user).
+		MailFoldersById(parentID).
+		ChildFolders().
+		Post(ctx, requestBody, nil)
+}
+
 // DeleteMailFolder removes a mail folder with the corresponding M365 ID  from the user's M365 Exchange account
 // Reference: https://docs.microsoft.com/en-us/graph/api/mailfolder-delete?view=graph-rest-1.0&tabs=http
 func DeleteMailFolder(ctx context.Context, gs graph.Service, user, folderID string) error {

src/internal/connector/graph_connector_test.go

@@ -309,17 +309,28 @@ func (suite *GraphConnectorIntegrationSuite) TestAccessOfInboxAllUsers() {
 // to create and remove folders within the tenant
 func (suite *GraphConnectorIntegrationSuite) TestCreateAndDeleteMailFolder() {
 	ctx := context.Background()
+	t := suite.T()
 	now := time.Now()
 	folderName := "TestFolder: " + common.FormatSimpleDateTime(now)
 	aFolder, err := exchange.CreateMailFolder(ctx, suite.connector.Service(), suite.user, folderName)
-	assert.NoError(suite.T(), err, support.ConnectorStackErrorTrace(err))
+	assert.NoError(t, err, support.ConnectorStackErrorTrace(err))
 
 	if aFolder != nil {
+		secondFolder, err := exchange.CreateMailFolderWithParent(
+			ctx,
+			suite.connector.Service(),
+			suite.user,
+			"SubFolder",
+			*aFolder.GetId(),
+		)
+		assert.NoError(t, err)
+		assert.True(t, *secondFolder.GetParentFolderId() == *aFolder.GetId())
+
 		err = exchange.DeleteMailFolder(ctx, suite.connector.Service(), suite.user, *aFolder.GetId())
-		assert.NoError(suite.T(), err)
+		assert.NoError(t, err)
 
 		if err != nil {
-			suite.T().Log(support.ConnectorStackErrorTrace(err))
+			t.Log(support.ConnectorStackErrorTrace(err))
 		}
 	}
 }