Set auth credentials when present to autheticate with Spring libs-snapshot Repository.

build.gradle

@@ -7,6 +7,15 @@ buildscript {
     mavenCentral()
     gradlePluginPortal()
     maven { url 'https://repo.spring.io/plugins-release' }
+    maven {
+      url 'https://repo.spring.io/plugins-snapshot'
+      if (project.hasProperty('artifactoryUsername')) {
+        credentials {
+          username "$artifactoryUsername"
+          password "$artifactoryPassword"
+        }
+      }
+    }
   }
 }