Introduce `append_related_issues` function and `IssueRelated` enum to manage related issue linking. Update Gitea action to utilize the new functionality for appending related issues in work package content. Add corresponding tests.
Added the "open" crate to Cargo.toml and corresponding dependencies to Cargo.lock. Updated the code to automatically open the newly created work package in the browser and handle potential failure cases gracefully.
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.
