Create outcome pairings

Start tracking an Outcomes pairing: a signal (a Discovery campaign's Brand Win Rate or Brand Share, or another outcome) and the outcome it may move (a connected source's sessions, key events or revenue, or an imported series' value, for all of it or the channel AI assistants referred), choosing from business_outcome_pairing_choices_get. It is measured at once from the history already stored and every day after. Pinned makes it the organization's one main test, tested alone (any other pin is lifted). Up to 25 pairings.