A parameter with choices named 'true' and 'false' are not handled correctly

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Exception noticed for a slivka service:
java.util.concurrent.CompletionException: java.lang.ClassCastException: class java.lang.Boolean cannot be cast to class java.lang.String (java.lang.Boolean and java.lang.String are in module java.base of loader 'bootstrap')
at java.util.concurrent.CompletableFuture.encodeThrowable(Unknown Source) ~[?:?]
at java.util.concurrent.CompletableFuture.completeThrowable(Unknown Source) [?:?]
at java.util.concurrent.CompletableFuture.uniHandle(Unknown Source) [?:?]
at java.util.concurrent.CompletableFuture$UniHandle.tryFire(Unknown Source) [?:?]
at java.util.concurrent.CompletableFuture$Completion.exec(Unknown Source) [?:?]
at java.util.concurrent.ForkJoinTask.doExec(Unknown Source) [?:?]
at java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(Unknown Source) [?:?]
at java.util.concurrent.ForkJoinPool.scan(Unknown Source) [?:?]
at java.util.concurrent.ForkJoinPool.runWorker(Unknown Source) [?:?]
at java.util.concurrent.ForkJoinWorkerThread.run(Unknown Source) [?:?]
Caused by: java.lang.ClassCastException: class java.lang.Boolean cannot be cast to class java.lang.String (java.lang.Boolean and java.lang.String are in module java.base of loader 'bootstrap')
at uk.ac.dundee.compbio.slivkaclient.Parameter$ChoiceParameter.readJSON(Parameter.java:252) ~[slivka-client.jar:?]
at uk.ac.dundee.compbio.slivkaclient.Parameter.fromJSON(Parameter.java:94) ~[slivka-client.jar:?]
at uk.ac.dundee.compbio.slivkaclient.SlivkaClientImpl.getServices(SlivkaClientImpl.java:115) ~[slivka-client.jar:?]
at jalview.ws2.client.slivka.SlivkaWSDiscoverer.fetchServices(SlivkaWSDiscoverer.java:103) ~[jalview.jar:2.12.0-d20260106]
at jalview.ws2.client.api.AbstractWebServiceDiscoverer.lambda$startDiscoverer$0(AbstractWebServiceDiscoverer.java:158) ~[jalview.jar:2.12.0-d20260106]
... 8 more
DEBUG - Discovery ended, state is 1

.. minimal service definition to reproduce will follow shortly

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Culprit is a choice parameter which has options 'true' or 'false' - so basically should be a boolean flag, but slivka allows those values as a choice anyhow in the service definition:
YAML:
{
"array": false,
"choices": [
true,
false
],
"default": null,
"description": "",
"id": "sprotein-sequence",
"name": "sprotein_sequence",
"required": false,
"type": "choice"
},

JSON: {"default":null,"array":false,"name":"sprotein_sequence","description":"","id":"sprotein-sequence","choices":[true,false],"type":"choice","required":false}

Thanks to @jvanp148 for noticing there was a problem !