add json.ml; add test.ml; timestamp jsont

src/types.ml

@@ -1,28 +1,15 @@
 (* https://docs.taler.net/core/api-common.html#tsref-type-ErrorDetail *)
-module ErrorDetail = struct
+module Error_detail = struct
   (* TODO GANA error codes
      https://git.gnunet.org/gana.git/tree/gnu-taler-error-codes/registry.rec *)
   type t = { code: int; hint: string option }
-
-  let make code hint = { code; hint }
-  let enc_code v = v.code
-  let enc_hint v = v.hint
-
-  let jsont =
-    Jsont.Object.map ~kind:"ErrorDetail" make
-    |> Jsont.Object.mem "code" Jsont.int ~enc:enc_code
-    |> Jsont.Object.opt_mem "hint" Jsont.(string) ~enc:enc_hint
-    |> Jsont.Object.finish
-
-  let to_string v = Jsont_bytesrw.encode_string jsont v |> Result.get_ok
-  let of_string v = Jsont_bytesrw.decode_string jsont v
 end
 
 module Timestamp = struct
   (* Seconds since epoch, or the special
      value "never" to represent an event that will
      never happen. *)
-  type t = Never | Seconds of int
+  type t = Never | Seconds of float
 end
 
 module Amount = struct