Show Open Issues - clicking opens a web page
Problem to solve
The plugin should show open GitLab issues for the current project.
Proposal
We create a mechanism of fetching issuables (Issues and MR's) that will be ready for more complex querying similar to the VS Code Extension Custom Queries but in the first iteration, we'll query only for open issues.
We'll then show these open issues in the GitLab ToolWindow. Clicking the issue in the tree view will open the issue in the browser.