Add option descriptions

Author: itzg

src/main/java/me/itzg/helpers/cache/CacheArgs.java

@@ -7,9 +7,13 @@
 
 @Data
 public class CacheArgs {
-    @Option(names = "--api-cache-ttl")
+    @Option(names = "--api-cache-ttl", paramLabel = "OPERATION=DURATION",
+        description = "Set individual operation TTLs"
+    )
     Map<String, Duration> cacheDurations;
 
-    @Option(names = "--api-cache-default-ttl", defaultValue = "P2D")
+    @Option(names = "--api-cache-default-ttl", defaultValue = "P2D", paramLabel = "DURATION",
+        description = "Set default/fallback TTL in ISO-8601 duration format.\nDefault: ${DEFAULT-VALUE}"
+    )
     Duration defaultCacheDuration;
 }