Doc Feedback: The customer handler doesn't work with the ThrottleHandler

Location : https://apim.docs.wso2.com/en/latest/develop/extending-api-manager/extending-gateway/writing-custom-handlers/

When enabling this handler, the throttling handler also needs to be disabled from the velocity template. Otherwise, the bellow throttling error will be there. If we can change the customer handler so the authentication header will be extracted from a custom header instead of the standard Authentication header, this issue will not be there.

java.lang.NullPointerException: null
	at org.wso2.carbon.apimgt.gateway.handlers.throttling.ThrottleHandler.doRoleBasedAccessThrottlingWithCEP_aroundBody0(ThrottleHandler.java:193) ~[org.wso2.carbon.apimgt.gateway_6.7.206.jar:?]
	at org.wso2.carbon.apimgt.gateway.handlers.throttling.ThrottleHandler.doRoleBasedAccessThrottlingWithCEP(ThrottleHandler.java:145) ~[org.wso2.carbon.apimgt.gateway_6.7.206.jar:?]
	at org.wso2.carbon.apimgt.gateway.handlers.throttling.ThrottleHandler.doThrottle_aroundBody12(ThrottleHandler.java:591) ~[org.wso2.carbon.apimgt.gateway_6.7.206.jar:?]
	at org.wso2.carbon.apimgt.gateway.handlers.throttling.ThrottleHandler.doThrottle(ThrottleHandler.java:568) ~[org.wso2.carbon.apimgt.gateway_6.7.206.jar:?]
	at org.wso2.carbon.apimgt.gateway.handlers.throttling.ThrottleHandler.handleRequest_aroundBody8(ThrottleHandler.java:528) ~[org.wso2.carbon.apimgt.gateway_6.7.206.jar:?]
	at org.wso2.carbon.apimgt.gateway.handlers.throttling.ThrottleHandler.handleRequest(ThrottleHandler.java:509) ~[org.wso2.carbon.apimgt.gateway_6.7.206.jar:?]
	at org.apache.synapse.rest.API.process(API.java:373) ~[synapse-core_2.1.7.wso2v183.jar:2.1.7-wso2v183]
	at org.apache.synapse.rest.RESTRequestHandler.apiProcessNonDefaultStrategy(RESTRequestHandler.java:144) ~[synapse-core_2.1.7.wso2v183.jar:2.1.7-wso2v183]
	at org.apache.synapse.rest.RESTRequestHandler.identifyAPI(RESTRequestHandler.java:164) ~[synapse-core_2.1.7.wso2v183.jar:2.1.7-wso2v183]
	at org.apache.synapse.rest.RESTRequestHandler.dispatchToAPI(RESTRequestHandler.java:95) ~[synapse-core_2.1.7.wso2v183.jar:2.1.7-wso2v183]
	at org.apache.synapse.rest.RESTRequestHandler.process(RESTRequestHandler.java:73) ~[synapse-core_2.1.7.wso2v183.jar:2.1.7-wso2v183]
	at org.apache.synapse.core.axis2.Axis2SynapseEnvironment.injectMessage(Axis2SynapseEnvironment.java:331) ~[synapse-core_2.1.7.wso2v183.jar:2.1.7-wso2v183]
	at org.apache.synapse.core.axis2.SynapseMessageReceiver.receive(SynapseMessageReceiver.java:99) ~[synapse-core_2.1.7.wso2v183.jar:2.1.7-wso2v183]
	at org.apache.axis2.engine.AxisEngine.receive(AxisEngine.java:180) ~[axis2_1.6.1.wso2v41.jar:?]
	at org.apache.synapse.transport.passthru.ServerWorker.processNonEntityEnclosingRESTHandler(ServerWorker.java:367) [synapse-nhttp-transport_2.1.7.wso2v183.jar:?]
	at org.apache.synapse.transport.passthru.ServerWorker.run(ServerWorker.java:188) [synapse-nhttp-transport_2.1.7.wso2v183.jar:?]
	at org.apache.axis2.transport.base.threads.NativeWorkerPool$1.run(NativeWorkerPool.java:172) [axis2_1.6.1.wso2v41.jar:?]
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [?:1.8.0_201]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [?:1.8.0_201]
	at java.lang.Thread.run(Thread.java:748) [?:1.8.0_201]

Start with the custom-handler documentation page and inspect the velocity template and ThrottleHandler.java around line 193. Reproduce the reported interaction between the customer handler and ThrottleHandler, then define the change needed so both handlers can be enabled without the reported throttling error.