OH3.1 Exception when using http binding

I am using the http binding with text config. When loading the thing I see the following exception in the openhab.log

2021-06-30 22:40:55.702 [INFO ] [el.core.internal.ModelRepositoryImpl] - Loading model 'http_publish.things'
2021-06-30 22:40:55.710 [WARN ] [re.config.core.internal.ConfigMapper] - Could not set field value for field 'headers': Can not set java.util.ArrayList field org.openhab.binding.http.internal.config.HttpThingConfig.headers to java.util.ImmutableCollections$List12
java.lang.IllegalArgumentException: Can not set java.util.ArrayList field org.openhab.binding.http.internal.config.HttpThingConfig.headers to java.util.ImmutableCollections$List12
        at jdk.internal.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:167) ~[?:?]
        at jdk.internal.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:171) ~[?:?]
        at jdk.internal.reflect.UnsafeObjectFieldAccessorImpl.set(UnsafeObjectFieldAccessorImpl.java:81) ~[?:?]
        at java.lang.reflect.Field.set(Field.java:780) ~[?:?]
        at org.openhab.core.config.core.internal.ConfigMapper.as(ConfigMapper.java:101) [bundleFile:?]
        at org.openhab.core.config.core.Configuration.as(Configuration.java:80) [bundleFile:?]
        at org.openhab.core.thing.binding.BaseThingHandler.getConfigAs(BaseThingHandler.java:218) [bundleFile:?]
        at org.openhab.binding.http.internal.HttpThingHandler.initialize(HttpThingHandler.java:139) [bundleFile:?]
        at org.openhab.core.thing.binding.BaseThingHandler.thingUpdated(BaseThingHandler.java:152) [bundleFile:?]
        at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:?]
        at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:?]
        at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:?]
        at java.lang.reflect.Method.invoke(Method.java:566) ~[?:?]
        at org.openhab.core.internal.common.AbstractInvocationHandler.invokeDirect(AbstractInvocationHandler.java:154) [bundleFile:?]
        at org.openhab.core.internal.common.Invocation.call(Invocation.java:52) [bundleFile:?]
        at java.util.concurrent.FutureTask.run(FutureTask.java:264) [?:?]
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) [?:?]
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) [?:?]
        at java.lang.Thread.run(Thread.java:829) [?:?]
2021-06-30 22:40:55.711 [INFO ] [nding.http.internal.HttpThingHandler] - Using the secure client for thing 'http:url:publish'.

My thing file looks like this:

Thing http:url:publish [

    baseURL = "https://www.$$$$$$$$$$$$$$$$$/import_test.php?", 
    commandMethod = "POST", 
    headers="X-Auth=$$$$$$$$$$$$$$$$$",
    refresh = 300
] {
    Channels:
        Type string : mainfrontdoorlockstateadv [
            stateExtension = "item=MainGF_Main_Frontdoor_LockState_Adv&type=str",
            mode="WRITEONLY"
        ]
}

I am not sure what I am doing wrong especially, I think it worked in OpenHAB 3.0

Ok, seems to be an issue in the OH3.1 binding…
It’s working if I change the line
headers="X-Auth=$$$$$$$$$$$$$$$$$",
to
headers="X-Auth=$$$$$$$$$$$$$$$$$","workaround=bla",

It seems to throw an exception if only one header is provided.

What’s the best place to report this issue?

Thank you! For documentation, I just opend an issue:

Thanks for pointing this out… I was struggling with the same problem and the error message HTTP protocol violation: Authentication challenge without WWW-Authenticate header although I provided the authentication header. Adding a second dummy entry solved the issue for me as well.
Thanks!