Route a new user to the best dedicated iMessage line
Returns the single best dedicated iMessage line to assign a new user to, load-balancing by active user count and recent growth. Lines provisioned less than 15 minutes ago are skipped while an older line exists: running Spectrum SDK instances discover new lines at token renewal, so routing users to a brand-new line could strand their messages on replicas that cannot see it yet. isBestAvailable is false when the returned line is the least-bad fallback — it holds more than 500 users or grew by more than 10 users in the last minute, meaning no genuinely healthy line was available. Returns 404 if the project owns no dedicated iMessage lines. Requires Authorization: Basic base64(projectId:projectSecret).
Path Parameters
^([0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[1-8][0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}|00000000-0000-0000-0000-000000000000|ffffffff-ffff-ffff-ffff-ffffffffffff)$