Add KVMap for MQTTContext and update Kafka filter

[suchen-sci]

No description provided.

[codecov-commenter]

Codecov Report

Merging #462 (d51abc7) into main (7548804) will decrease coverage by 0.31%.
The diff coverage is 67.10%.

@@            Coverage Diff             @@
##             main     #462      +/-   ##
==========================================
- Coverage   80.29%   79.97%   -0.32%     
==========================================
  Files          73       73              
  Lines        8275     8321      +46     
==========================================
+ Hits         6644     6655      +11     
- Misses       1265     1297      +32     
- Partials      366      369       +3     

Impacted Files	Coverage Δ
pkg/filter/kafka/kafka.go	56.73% <61.01%> (+0.27%)	⬆️
pkg/filter/topicmapper/topicmapper.go	48.64% <66.66%> (ø)
pkg/filter/connectcontrol/connectcontrol.go	96.10% <100.00%> (ø)
pkg/filter/mqttclientauth/mqttauth.go	83.56% <100.00%> (ø)
pkg/cluster/layout.go	89.47% <0.00%> (-10.53%)	⬇️
pkg/object/mqttproxy/session.go	74.23% <0.00%> (-7.98%)	⬇️

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[zhao-kun]

LGTM