Because:
- Pairing v2 switched on from the pairingVersion Firefox reports in
fxa_status, which follows a Firefox pref default, so the rollout
waited on Firefox flipping the pref rather than on us.
- pairing.ios_handoff answered the same question, whether Firefox iOS
is ready for v2, a second way.
This commit:
- Adds pairing.v2_min_version.{ios,android,desktop}; a set platform is
decided from the Firefox major version in the user agent, an unset one
still defers to fxa_status.
- Routes /pair and /connect_another_device through a shared
isPairingV2Enabled gate.
- Replaces pairing.ios_handoff with whether an iOS minimum is configured.
- Covers the gate with unit tests and both pages with wiring tests.
- Updates the dev-launcher and functional-test pairing notes.
Closes #FXA-14582