Personally I think you should just ditch the idea altogether.
Whether it is your intention or not, through this, you obtain email addresses of every member on every discourse forum out there (unless the admin opts out). Although we have no reason to distrust you, should Discourse change hands in future the new owners could use the info to start competing sites.
Opting out doesn’t fully protect those installs either - it poses a threat to all forums in all niches; even if you have the largest forum in your niche, users of a few hundred other forums in your niche joined together could well prove difficult to compete against.
Sorry to be so negative about this issue - but it is the only thing I have actually disliked about Discourse.