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 400 users or grew by more than 2 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)$