build: use gradle version catalogs

This commit keeps all versions in one location, for reference throughout
various build scripts.

https://docs.gradle.org/current/userguide/platforms.html

build.gradle

@@ -2,8 +2,7 @@ plugins {
   // Facilitates Java compilation
   id 'java'
   // For formatting source-code
-  // NOTE: This is the maximum version that will work with JDK 8.
-  id 'com.diffplug.spotless' version '6.12.0'
+  alias(libs.plugins.spotless)
 }
 
 // Tasks not related to build are split out into their own gradle scripts
@@ -21,7 +20,7 @@ dependencies {
   // Ensure gradle is aware of the patched_client.jar dependency
   implementation files('patched_client.jar')
   // Used to find/populate scripts
-  implementation group: 'org.reflections', name: 'reflections', version: '0.10.2'
+  implementation libs.reflections
 }
 
 tasks.named('jar') {

gradle/libs.versions.toml

@@ -0,0 +1,11 @@
+[versions]
+spotless = '6.12.0' # maximum version that will work with JDK 8.
+google-java-format = '1.7' # maximum version that will work with JDK 8.
+reflections = '0.10.2'
+
+[plugins]
+spotless = { id = 'com.diffplug.spotless', version.ref = 'spotless' }
+google-java-format = { id = 'com.google.googlejavaformat', version.ref = 'google-java-format' }
+
+[libraries]
+reflections = { module = 'org.reflections:reflections', version.ref = 'reflections' }

spotless.gradle

@@ -15,8 +15,7 @@ spotless {
     removeUnusedImports()
     // Follow the Google Java formatting guide
     // ref: https://google.github.io/styleguide/javaguide.html
-    // NOTE: This is the maximum version that will work with JDK 8.
-    googleJavaFormat('1.7')
+    googleJavaFormat("${libs.versions.google.java.format.get()}")
     // Fix formatting of type annotations
     formatAnnotations()
   }