Feature: Environment variable for Opt-Outs to be shared across all organizations on the instance

[schuyler1d]

Sometimes a single real organization will have a spoke instance, but want to divide camaigns and texters for management purposes.

The current blocker is that opt-outs are only per-organization, so an opt-out that occurs from one organization will not get opted-out on another campaign.

Thus we should have an environment variable
OPTOUTS_SHARE_ALL_ORGS
when true:

• Opt-out queries will not filter by organization
• creating an opt-out should mark all current contacts across organizations (not just across campaigns, like now)

One possibility while working on this would be to remove/ignore the campaign_contact.is_opted_out column and change all queries to JOIN on opt_out by cell instead.

Also please be conscious of parallel scaling work that has begun:
https://github.com/MoveOnOrg/Spoke/pull/869

[shakalee14]

Fixed with #901