Rate limits apply per client by default

Rate-limit actions that use the Default scope now give each client IP its own bucket. Previously the default bucket was shared by all clients, so one client could use up a limit, such as a login limit, for everyone. IPv6 clients are grouped by /64, so rotating addresses within one allocation no longer gets a fresh allowance.

To keep one bucket per rule, choose an explicit empty scope. Requires proxy v0.27.0 or newer.