Feature Request: use external_id for VAN action handler when lists are manually uploaded and VanID is not present

[mayefsky]

I've had a couple of users now run into problems with the VAN action handler when they upload a manual list with an external_id but expect the action handling to work. The VAN action handler expects VanID instead, so it doesn't sync.
I realize it's not too too common for folks to use the VAN integration without using the contact loader, but I also would hope falling back to external_id when there's no VanID might be an easy add. (Disclaimer I am also still 8.0 until later this week; I didn't see this as something that was part of anything in 8.1 or 9.0 but possible I missed it).

@lperson --not a big item but just opening in case this sounds reasonable/is an easy add for you at some point; thank you!

[maxkc]

Just an FYI - you may want to make sure this is validated as a numeric value prior to upload. VAN throws an annoying error if you try and use an alphanumeric value for VANID in anything /people/{vanId} related.

Known bug but low priority fix for now.