The first step in implementing this would be to do the following:

• Add an enum that specifies the supported issue types.
• Add a type field to the issue table.
• Support a type file in the View Issues table.
• Support a type field in the view, update, report pages (simple/advanced).
• Support the type field in the filters.
• Add an upgrade step that adds the field to the schema and default it for existing issues.
• The first stage of implementing this will assume that all issue types will have the same fields (i.e. attributes of an issue doesn't depend on it's type).