Provide relevant default values for Enums

This commits adds manual metadata for enums that have a default value
since the annotation processor is not able to detect that yet.

Closes gh-7890

spring-boot/src/main/resources/META-INF/additional-spring-configuration-metadata.json

@@ -145,6 +145,10 @@
     "sourceType": "org.springframework.boot.context.config.ConfigFileApplicationListener",
     "description": "Config file locations."
   },
+  {
+    "name": "spring.jta.atomikos.properties.console-log-level",
+    "defaultValue": "warn"
+  },
   {
     "name": "spring.main.banner-mode",
     "type": "org.springframework.boot.Banner$Mode",