Upgrade Gradle to 8.7 and fix deprecations (#167)

Update Gradle to 8.7 and fixes deprecation warnings.

build.gradle

@@ -18,26 +18,30 @@ import static java.nio.file.StandardCopyOption.REPLACE_EXISTING
  * specific language governing permissions and limitations
  * under the License.
  */
-apply plugin: "java"
-apply plugin: 'maven-publish'
-apply plugin: "distribution"
-apply plugin: "idea"
+ buildscript {
+    repositories {
+        mavenCentral()
+    }
+}
+
+plugins {
+  id 'java'
+  id 'maven-publish'
+  id 'distribution'
+  id 'idea'
+}
 
 group "org.logstash.integrations"
 
-sourceCompatibility = JavaVersion.VERSION_1_8
+java {
+  sourceCompatibility = JavaVersion.VERSION_1_8
+}
 
 // given https://docs.confluent.io/current/installation/versions-interoperability.html matrix
 // Confluent Platform 7.4.x is Apache Kafka 3.4.x
 String confluentKafkaVersion = '7.4.0'
 String apacheKafkaVersion = '3.4.1'
 
-buildscript {
-    repositories {
-        mavenCentral()
-    }
-}
-
 repositories {
     mavenCentral()
     maven {

gradle/wrapper/gradle-wrapper.properties

@@ -1,5 +1,7 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-7.6-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.7-bin.zip
+networkTimeout=10000
+validateDistributionUrl=true
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists