Refactor Gitea client and improve issue handling

Update the authorization header format in the Gitea client. Enhance issue details in work package creation and make `number` field public in the `Issue` struct.

src/gitea/action.rs

@@ -47,7 +47,7 @@ impl Issue2WorkActionTrait for GiteaAction {
 
 fn create_work_package_from_issue(issue: &Issue, assignee: Option<User>) -> WorkPackageWriter {
     WorkPackageWriter {
-        subject: format!("{} ({})", issue.title, issue.repository.full_name),
+        subject: format!("{} ({}/{})", issue.title, issue.repository.full_name, issue.number),
         work_type: "TASK".into(),
         description: crate::openproject::work::DescriptionWriter {
             format: "markdown".into(),