Remove deprecated Configuration.setVisible(boolean) call (Gradle 9.8) (#271)

* Remove deprecated Configuration.setVisible(boolean) call

The per-project producer configuration called `isVisible = false`, which
Gradle deprecated in 9.8.0-milestone-2 (scheduled for removal in Gradle 11).
Builds that fail on deprecation warnings (`org.gradle.warning.mode=fail`) break
as soon as a project applying the nmcp plugin is configured.

The `visible` property no longer has any meaningful effect on the build, and
the internal `nmcpProducer` configuration is already kept out of resolution via
`canBeConsumed=true`/`canBeResolved=false`, so the call can be removed without
changing behaviour on any supported Gradle version.

* Guard Configuration.setVisible(boolean) behind a Gradle < 9.8 check

Per review feedback: keep the `isVisible = false` behaviour on Gradle
versions where it still matters (so publications aren't published as part of
`assemble`), and only skip it on Gradle 9.8+ where the property is deprecated
and inert. This avoids the deprecation warning on 9.8+ while preserving the
original behaviour on older Gradle versions.

Author: breskeby

nmcp/src/main/kotlin/nmcp/internal/DefaultNmcpExtension.kt

@@ -10,6 +10,7 @@ import org.gradle.api.Action
 import org.gradle.api.Project
 import org.gradle.api.publish.PublishingExtension
 import org.gradle.api.publish.maven.MavenPublication
+import org.gradle.util.GradleVersion
 
 @GExtension(pluginId = "com.gradleup.nmcp", publicType = NmcpExtension::class, extensionName = nmcpExtensionName)
 internal abstract class DefaultNmcpExtension(private val project: Project): NmcpExtension {
@@ -25,7 +26,12 @@ internal abstract class DefaultNmcpExtension(private val project: Project): Nmcp
             it.isCanBeConsumed = true
             it.isCanBeResolved = false
             // See https://github.com/GradleUp/nmcp/issues/2
-            it.isVisible = false
+            // Without this, the publications end up being published as part of `assemble`.
+            // `Configuration.setVisible(boolean)` is deprecated as of Gradle 9.8 (and inert since),
+            // so only call it on older Gradle versions to stay warning-clean on 9.8+.
+            if (GradleVersion.current() < GradleVersion.version("9.8")) {
+                it.isVisible = false
+            }
 
             it.configureAttributes(project)
         }