conditional JSON options for iOS/Android (#318)

* conditional JSON options for iOS/Android

* update cabal file

simplexmq.cabal

@@ -27,6 +27,9 @@ extra-source-files:
     README.md
     CHANGELOG.md
 
+if (os(android))
+  ghc-option: -DANDROID
+
 library
   exposed-modules:
       Simplex.Messaging.Agent

src/Simplex/Messaging/Parsers.hs

@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP #-}
 {-# LANGUAGE LambdaCase #-}
 {-# LANGUAGE OverloadedStrings #-}
 
@@ -97,7 +98,11 @@ enumJSON tagModifier =
     }
 
 sumTypeJSON :: (String -> String) -> J.Options
+#if defined(ANDROID)
+sumTypeJSON = taggedObjectJSON
+#else
 sumTypeJSON = singleFieldJSON
+#endif
 
 taggedObjectJSON :: (String -> String) -> J.Options
 taggedObjectJSON tagModifier =