Code review comment for lp:~wallyworld/launchpad/additional-affiliation-types-798764

I have put this new functionality behind a new eature flag: disclosure.personpicker_affiliation.enabled
Previously, this work was behind the existing disclosure.enhance_picker.enabled flag.

The reason is that there are questions over the performance in terms of the number of selects from the TeamParticipation table. The enhance_picker feature flag is on for production and I don't want to risk breaking lp.net with this new work.