refactor maven central user/pass properties, to avoid weird Gradle er…

…ror:

The following Gradle properties are missing for 'SonatypeRelease' credentials:
- SonatypeReleaseUsername
- SonatypeReleasePassword

buildSrc/src/main/kotlin/buildsrc/conventions/maven-publishing.gradle.kts

@@ -57,10 +57,15 @@ publishing {
 //region Maven Central publishing/signing
 publishing {
   repositories {
-    if (mavenPublishing.mavenCentralCredentials.isPresent) {
+    val mavenCentralUsername = mavenPublishing.mavenCentralUsername.orNull
+    val mavenCentralPassword = mavenPublishing.mavenCentralPassword.orNull
+    if (!mavenCentralUsername.isNullOrBlank() && !mavenCentralPassword.isNullOrBlank()) {
       maven(mavenPublishing.sonatypeReleaseUrl) {
         name = "SonatypeRelease"
-        credentials(mavenPublishing.mavenCentralCredentials.get())
+        credentials {
+          username = mavenCentralUsername
+          password = mavenCentralPassword
+        }
       }
     }
   }

buildSrc/src/main/kotlin/buildsrc/settings/MavenPublishingSettings.kt

@@ -2,9 +2,7 @@ package buildsrc.settings
 
 import java.io.File
 import javax.inject.Inject
-import org.gradle.api.Action
 import org.gradle.api.Project
-import org.gradle.api.artifacts.repositories.PasswordCredentials
 import org.gradle.api.provider.Provider
 import org.gradle.api.provider.ProviderFactory
 import org.gradle.kotlin.dsl.*
@@ -30,21 +28,13 @@ abstract class MavenPublishingSettings @Inject constructor(
       }
     }
 
-  private val mavenCentralUsername: Provider<String> =
+  val mavenCentralUsername: Provider<String> =
     d2Prop("mavenCentralUsername")
       .orElse(providers.environmentVariable("MAVEN_SONATYPE_USERNAME"))
-  private val mavenCentralPassword: Provider<String> =
+  val mavenCentralPassword: Provider<String> =
     d2Prop("mavenCentralPassword")
       .orElse(providers.environmentVariable("MAVEN_SONATYPE_PASSWORD"))
 
-  val mavenCentralCredentials: Provider<Action<PasswordCredentials>> =
-    providers.zip(mavenCentralUsername, mavenCentralPassword) { user, pass ->
-      Action<PasswordCredentials> {
-        username = user
-        password = pass
-      }
-    }
-
   val signingKeyId: Provider<String> =
     d2Prop("signing.keyId")
       .orElse(providers.environmentVariable("MAVEN_SONATYPE_SIGNING_KEY_ID"))