Store GitHub issue information in the database and display it

[Erethon]

At the moment, we don't store the GitHub issue ID (or org/project information) when we create a GitHub issue from a draft suggestion. Due to this, we can't display a permalink to a GitHub issue in the issues view. The only way to correlate between security tracker issues and created GitHub issues, is to get this information from the GitHub issue description.

Attached is a screenshot of the current issue view, notice there's no link to a GitHub issue.

We should:

1. Start storing this information
2. Display it on the issue(s) view