Update to gradle-nexus publish-plugin (#520)

- remove "artifacts" and add "artifact" to have javadoc and sources build
- invoke `./gradlew publishToMavenLocal`: build and sign artifacts and put
  these into local maven repository
- invoke `./gradlew publishToSonatype` to build, sign and upload artifacts
  to sonatype

Author: dr0i

build.gradle

@@ -20,7 +20,7 @@ plugins {
   id 'org.ajoberstar.grgit' version '2.3.0'
   //id 'org.ec4j.editorconfig' version '0.0.3'
   id 'org.sonarqube' version '2.6.2'
-  id 'io.codearte.nexus-staging' version '0.30.0'
+  id 'io.github.gradle-nexus.publish-plugin' version '1.3.0'
 }
 
 subprojects {
@@ -128,11 +128,6 @@ subprojects {
     }
   }
 
-  artifacts {
-    archives sourceJar
-    archives javadocJar
-  }
-
   checkstyle {
     toolVersion '8.30'
     checkstyleTest.enabled = false
@@ -216,6 +211,8 @@ subprojects {
               url = 'https://github.com/metafacture/metafacture-core/actions'
             }
           }
+          artifact(sourceJar)
+          artifact(javadocJar)
         }
       }
     }
@@ -237,15 +234,6 @@ subprojects {
           }
         }
       }
-      else if (project.hasProperty('snapshotRepositoryUrl')) {
-        maven {
-          url = snapshotRepositoryUrl
-          credentials {
-            username = snapshotRepositoryUser
-            password = snapshotRepositoryPassword
-          }
-        }
-      }
     }
   }
 
@@ -268,24 +256,12 @@ sonarqube {
   }
 }
 
-nexusStaging {
-  if (project.hasProperty('stagingServerUrl')) {
-    serverUrl = stagingServerUrl
-  }
-  if (project.hasProperty('releaseRepositoryUser')) {
-    username = releaseRepositoryUser
-    password = releaseRepositoryPassword
+nexusPublishing {
+  repositories {
+    sonatype ()
   }
 }
 
-tasks.closeRepository.onlyIf {
-  rootProject.scmInfo.isRelease()
-}
-
-tasks.releaseRepository.onlyIf {
-  rootProject.scmInfo.isRelease()
-}
-
 class ScmInfo {
   def version
   def tag