chore: Add code formatter

Author: lukaszsocha2

build.gradle

@@ -1,5 +1,6 @@
 plugins {
     id "com.github.nbaztec.coveralls-jacoco" version "1.2.14"
+    id "com.diffplug.spotless" version "6.2.0"
     id "checkstyle"
     id "jacoco"
     id "java"
@@ -151,6 +152,13 @@ artifacts {
     archives sourcesJar, javadocJar
 }
 
+spotless {
+    java {
+        googleJavaFormat "1.7"
+        target "src/**/*.java"
+    }
+}
+
 test {
     useJUnit {
         excludeCategories "com.box.sdk.IntegrationTestJWT"