[BUG] SUBACK always grants QoS 0, ignoring the requested QoS
Open
plugin: mqtt
priority: high
type: bug
- Dominant language
- Java
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Description
## Description
The SUBACK grant list is built by hard-coding `MqttQoS.AT_MOST_ONCE.value()` for every topic, never reading `topicSub.qualityOfService()`.
## Location
- `shenyu-protocol/shenyu-protocol-mqtt/src/main/java/org/apache/shenyu/protocol/mqtt/Subscribe.java:90-94` (line 93 hard-codes `AT_MOST_ONCE.value()`)
## Impact
A client subscribing at QoS 1 or 2 is told it was granted QoS 0 and (see H-27) will only ever receive QoS 0 delivery. Violates MQTT-3.8.4/3.9.
## Suggested fix
`qos.add(topicSub.qualityOfService().value())` (after the FAILURE filter).
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