Email needs to be sent to trackers on identity change

If I follow user X and he/she updates their identity, I should get an intelligent email summarizing this change so I can choose to re-track them or not.

It should say what the changes are.

As for email settings, there's a setting for this already programmed and available to change on the subscription pages.

Start by reviewing the existing email setting and subscription pages mentioned in the issue, then trace how identity changes and tracker notifications are handled. Done means trackers receive an email that summarizes the identity changes and can choose whether to re-track the user.

Written by the indexing model from the issue text.