rfc: apply suggestions from review

Co-Authored-By: Dominik Froehlich <dominik.froehlich@sap.com>

toc/rfc/rfc-draft-generic-per-route-features.md

@@ -27,6 +27,11 @@ SHOULD ignore the contents of the map except gorouter, cloud controller and cf C
 the map and its values accordingly. Other components MAY limit the size of the map or size of
 keys / values for technical reasons.
 
+The following constraints apply (types are as specified in [RFC 8259](https://rfc-editor.org/rfc/rfc8259)):
+* The map MUST be representable as an object.
+* The map MUST only use strings as keys.
+* The map MUST only use numbers, strings and the literal values `true` and `false` as values.
+
 ### Required Changes
 
 #### CLI
@@ -62,6 +67,37 @@ with the generic logic for supporting the new map.
 
 As new features are specified they MUST be implemented in gorouter.
 
+Example `router.register` NATS message containing additional options (field names and values are not
+final):
+
+```json
+{
+  "host": "127.0.0.1",
+  "port": 4567,
+  "tls_port": 1234,
+  "protocol": "http1",
+  "uris": [
+    "my_first_url.localhost.routing.cf-app.com",
+    "my_second_url.localhost.routing.cf-app.com/some-path"
+  ],
+  "tags": {
+    "another_key": "another_value",
+    "some_key": "some_value"
+  },
+  "options": {
+    "lb-algo": "least-conn",
+    "conn-limit": 100,
+    "cookie": "my-session-cookie",
+    "trim-path": true
+  },
+  "app": "some_app_guid",
+  "stale_threshold_in_seconds": 120,
+  "private_instance_id": "some_app_instance_id",
+  "isolation_segment": "some_iso_seg_name",
+  "server_cert_domain_san": "some_subject_alternative_name"
+}
+```
+
 To-Do:
 * Can we somehow report errors from gorouter back to the user?