Feature Request: mobilecommons action-handler should allow for per-campaign opt-in paths

[ibrand]

Problem Our organizer would like to be able to measure the signups to our broadcast lists for different kinds of campaigns and entities. One of the easiest ways to do this would be if they could use different opt in paths for different entities and campaigns and use the measurement tools that are built into mobile commons to see how those different paths are performing.

Solution We should add per-campaign opt-in paths to the mobilecommons action-handler.

Context We already have the Mobilecommons (UMC) action-handler that syncs keywords to opt into mobile commons, but currently it uses a per instance level opt in path or a CSV addition. So if we can thread in an opt in path that gets entered into the action-handler itself or in the campaign settings then we could solve this.