Refactor the SBDG Gradle build script.

Declare the Spring plugins-release repository in buildscript.

Add authentication (credentials) to the Spring plugins-snapshot repository declaration in buildscript.

Redefined the snapshotBuild, milestoneBuild and releaseBuild project extensions properties in terms of the Utils Groovy class from Spring Build Conventions Gradle Plugins.

build.gradle

@@ -1,7 +1,19 @@
+import io.spring.gradle.convention.Utils
+
 buildscript {
 	repositories {
+		mavenCentral()
 		gradlePluginPortal()
-		maven { url 'https://repo.spring.io/plugins-snapshot' }
+		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"
+				}
+			}
+		}
 	}
 	dependencies {
 		classpath 'io.spring.gradle:spring-build-conventions:0.0.38'
@@ -43,8 +55,8 @@ description = 'Spring Boot for Apache Geode'
 //ext['spring-data-bom.version'] = "$springDataBomVersion"
 //ext['spring-session-bom.version'] = "$springSessionBomVersion"
 
-ext.snapshotBuild = version.endsWith('SNAPSHOT')
-ext.releaseBuild = version.endsWith('RELEASE')
-ext.milestoneBuild = !(releaseBuild || snapshotBuild)
+ext.snapshotBuild = Utils.isSnapshot(project)
+ext.milestoneBuild = Utils.isMilestone(project)
+ext.releaseBuild = Utils.isRelease(project)
 
 ext.MAVEN_POM_EDITOR_GRADLE = "$rootDir/gradle/maven-pom-editor.gradle"