docs: javadoc on configuration service (#1232)

Co-authored-by: Chris Laprun <[email protected]>

Author: csviri

operator-framework-core/src/main/java/io/javaoperatorsdk/operator/api/config/ConfigurationServiceProvider.java

@@ -2,6 +2,10 @@
 
 import java.util.function.Consumer;
 
+/**
+ * For internal usage only, to avoid passing the operator configuration around. Preferred way to get
+ * to the ConfigurationService is via the reconciliation context.
+ */
 public class ConfigurationServiceProvider {
   static final ConfigurationService DEFAULT =
       new BaseConfigurationService(Utils.loadFromProperties());