Update to Spring Boot 2.5.9

Closes gh-608

gradle.properties

@@ -1,5 +1,5 @@
 version=0.2.2-SNAPSHOT
-springBootVersion=2.5.7
+springBootVersion=2.5.9
 org.gradle.jvmargs=-Xmx3g -XX:MaxPermSize=2048m -XX:+HeapDumpOnOutOfMemoryError
 org.gradle.parallel=true
 org.gradle.caching=true