add get-earliest-available-block-slot to debug tool

Signed-off-by: Gabriel Fukushima <gabrielfukushima@gmail.com>

teku/src/main/java/tech/pegasys/teku/cli/subcommand/debug/DebugDbCommand.java

@@ -142,6 +142,29 @@ public int getFinalizedState(
     }
   }
 
+  @Command(
+          name = "get-earliest-available-block-slot",
+          description = "Get the finalized state, if available, as SSZ",
+          mixinStandardHelpOptions = true,
+          showDefaultValues = true,
+          abbreviateSynopsis = true,
+          versionProvider = PicoCliVersionProvider.class,
+          synopsisHeading = "%n",
+          descriptionHeading = "%nDescription:%n%n",
+          optionListHeading = "%nOptions:%n",
+          footerHeading = "%n",
+          footer = "Teku is licensed under the Apache License 2.0")
+  public int getEarliestAvailableBlockSlot(
+          @Mixin final BeaconNodeDataOptions beaconNodeDataOptions,
+          @Mixin final Eth2NetworkOptions eth2NetworkOptions)
+          throws Exception {
+    try (final Database database = createDatabase(beaconNodeDataOptions, eth2NetworkOptions)) {
+      Optional<UInt64> earliestAvailableBlockSlot = database.getEarliestAvailableBlockSlot();
+        earliestAvailableBlockSlot.ifPresent(System.out::println);
+    }
+    return 0;
+  }
+
   @Command(
       name = "get-finalized-state-indices",
       description = "Display the slots of finalized states that are stored.",
@@ -868,4 +891,5 @@ private int writeBlock(final Path outputFile, final Optional<SignedBeaconBlock>
     }
     return 0;
   }
+
 }