gorouter drops hash-based route registrations — hash_balance no longer parsed when sent as a JSON string (regression introduced in v0.386.0 / #535)

[a18e]

Current behavior

Since v0.386.0, gorouter fails to unmarshal router.register NATS messages for any route configured with hash-based load balancing (loadbalancing: hash) that includes a hash_balance factor. The message is rejected as a validation error and dropped, so the endpoint is never registered — the route becomes unreachable (404 / stale until TTL expiry) even though the app and the registration message are healthy.

Observed log (gorouter.subscriber):

{"message":"validation-error","source":"gorouter.subscriber","data":{
  "error":"json: cannot unmarshal string into Go struct field RegistryMessageOpts.options.hash_balance of type float64",
  "payload":"{\"host\":\"10.0.73.2\",\"port\":0,\"tls_port\":61000,\"uris\":[\"...cf...sapcloud.io\"],\"protocol\":\"http1\",\"app\":\"e2483c52-...\",...,\"options\":{\"loadbalancing\":\"hash\",\"hash_header\":\"http-header-name\",\"hash_balance\":\"1.2\"}}",
  "subject":"router.register"}}

Desired behavior

gorouter should again accept hash_balance when it arrives as a JSON string, matching the wire format that Cloud Controller and route-emitter actually produce.

Fix WIP: #584

Affected Version

v0.386.0 through v0.393.0 (latest). Introduced by commit 02a2a93 (PR #535); last unaffected release: v0.385.0.