feat(6178): support enums as integers in jruby

ruby/src/main/java/com/google/protobuf/jruby/RubyMessage.java

@@ -669,6 +669,7 @@ public class RubyMessage extends RubyObject {
    * @param options [Hash] options for the decoder
    *  preserve_proto_fieldnames: set true to use original fieldnames (default is to camelCase)
    *  emit_defaults: set true to emit 0/false values (default is to omit them)
+   *  enums_as_integers: set true to emit enum values as integer (default is string)
    */
   @JRubyMethod(name = "encode_json", required = 1, optional = 1, meta = true)
   public static IRubyObject encodeJson(
@@ -690,6 +691,7 @@ public class RubyMessage extends RubyObject {
 
       IRubyObject emitDefaults = options.fastARef(runtime.newSymbol("emit_defaults"));
       IRubyObject preserveNames = options.fastARef(runtime.newSymbol("preserve_proto_fieldnames"));
+      IRubyObject enumAsIntegers = options.fastARef(runtime.newSymbol("enums_as_integers"));
 
       if (emitDefaults != null && emitDefaults.isTrue()) {
         printer = printer.includingDefaultValueFields();
@@ -698,6 +700,10 @@ public class RubyMessage extends RubyObject {
       if (preserveNames != null && preserveNames.isTrue()) {
         printer = printer.preservingProtoFieldNames();
       }
+      
+      if (enumAsIntegers != null && printingEnumsAsInts.isTrue()) {
+        printer = printer.printingEnumsAsInts();
+      }
     }
     printer =
         printer.usingTypeRegistry(