fix: golangci-lint warnings and tests

[MaxBreida]

This PR fixes:

• all kinds of golangci-lint warnings and errors
• compareVersions had dead code
• PolicyRepresentation unrecognized field "clients" error 👇

2025-02-04 12:30:16,312 ERROR [org.keycloak.services.error.KeycloakErrorHandler] (executor-thread-1) Uncaught server error: java.lang.RuntimeException: Failed to deserialize representation
	at org.keycloak.authorization.admin.PolicyService.doCreateRepresentation(PolicyService.java:135)
	at org.keycloak.authorization.admin.PolicyService.create(PolicyService.java:119)
	at org.keycloak.authorization.admin.PolicyService$quarkusrestinvoker$create_195cd61c18e9138a5e834481c705d4fd435d9cb0.invoke(Unknown Source)
	at org.jboss.resteasy.reactive.server.handlers.InvocationHandler.handle(InvocationHandler.java:29)
	at io.quarkus.resteasy.reactive.server.runtime.QuarkusResteasyReactiveRequestContext.invokeHandler(QuarkusResteasyReactiveRequestContext.java:141)
	at org.jboss.resteasy.reactive.common.core.AbstractResteasyReactiveContext.run(AbstractResteasyReactiveContext.java:147)
	at io.quarkus.vertx.core.runtime.VertxCoreRecorder$14.runWith(VertxCoreRecorder.java:582)
	at org.jboss.threads.EnhancedQueueExecutor$Task.run(EnhancedQueueExecutor.java:2513)
	at org.jboss.threads.EnhancedQueueExecutor$ThreadBody.run(EnhancedQueueExecutor.java:1538)
	at org.jboss.threads.DelegatingRunnable.run(DelegatingRunnable.java:29)
	at org.jboss.threads.ThreadLocalResettingRunnable.run(ThreadLocalResettingRunnable.java:29)
	at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
	at java.base/java.lang.Thread.run(Thread.java:1583)
Caused by: com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "clients" (class org.keycloak.representations.idm.authorization.PolicyRepresentation), not marked as ignorable (13 known properties: "config", "resources", "scopesData", "name", "decisionStrategy", "policies", "owner", "type", "id", "description", "logic", "scopes", "resourcesData"])
 at [Source: REDACTED (`StreamReadFeature.INCLUDE_SOURCE_IN_LOCATION` disabled); line: 1, column: 108] (through reference chain: org.keycloak.representations.idm.authorization.PolicyRepresentation["clients"])
	at com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException.from(UnrecognizedPropertyException.java:61)
	at com.fasterxml.jackson.databind.DeserializationContext.handleUnknownProperty(DeserializationContext.java:1153)
	at com.fasterxml.jackson.databind.deser.std.StdDeserializer.handleUnknownProperty(StdDeserializer.java:2241)
	at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.handleUnknownProperty(BeanDeserializerBase.java:1793)
	at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.handleUnknownVanilla(BeanDeserializerBase.java:1771)
	at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:316)
	at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:177)
	at com.fasterxml.jackson.databind.deser.DefaultDeserializationContext.readRootValue(DefaultDeserializationContext.java:342)
	at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4905)
	at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3848)
	at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3816)
	at org.keycloak.util.JsonSerialization.readValue(JsonSerialization.java:77)
	at org.keycloak.authorization.admin.PolicyService.doCreateRepresentation(PolicyService.java:133)
	... 12 more

also not found in docs: https://www.keycloak.org/docs-api/latest/rest-api/index.html#PolicyRepresentation

This change probably warrants a major version upgrade as it's a breaking change in the PolicyRepresenation model