Make Rails EnumType handle serializing pre-serialized values (#256)

Co-authored-by: Stephen Margheim <[email protected]>

lib/literal/rails/enum_type.rb

@@ -22,9 +22,13 @@ def serialize(value)
 		when @enum
 			value.value
 		else
-			raise Literal::ArgumentError.new(
-				"Invalid value: #{value.inspect}. Expected an #{@enum.inspect}.",
-			)
+			if @enum[value]
+				value
+			else
+				raise Literal::ArgumentError.new(
+					"Invalid value: #{value.inspect}. Expected an #{@enum.inspect}.",
+				)
+			end
 		end
 	end