[FEATURE] Add support for grouping by tag

[p-mcgowan]

Is your feature request related to a problem? Please describe.
Segement / path grouping is cool, but would be nice to add support for grouping by tag (first if multiple), since the structure of the swagger / routing may not reflect groupings of domain logic

Describe the solution you'd like
Add option which, when provided, overrides segment grouping and uses the tag item to group domains

Describe alternatives you've considered
Reorganizing the swagger