Update Spring Boot to 2.5.2

Issue gh-344

gradle.properties

@@ -1,5 +1,5 @@
 version=0.1.2-SNAPSHOT
-springBootVersion=2.4.5
+springBootVersion=2.5.2
 org.gradle.jvmargs=-Xmx3g -XX:MaxPermSize=2048m -XX:+HeapDumpOnOutOfMemoryError
 org.gradle.parallel=true
 org.gradle.caching=true