offline tool: add wire-fee cmd

src/api.ml

@@ -525,9 +525,6 @@ end
 module WireFeeSetupMessage = struct
   type t = {
     wire_method: string;
-    (* TODO over which struct?
-       Signature using the exchange's offline key
-       with purpose TALER_SIGNATURE_MASTER_WIRE_FEES *)
     master_sig_wire: MasterWireFee.t;
     fee_start: Timestamp.t;
     fee_end: Timestamp.t;

src/http_management.ml

@@ -407,8 +407,19 @@ module Wire_fee = struct
     match wire_fees with
     | [] ->
         let+ () = Pg.insert_wire_fee db_conn v |> unwrap_err_caqti in
+        Logs.info (fun m -> m "added wire fee");
         ()
-    | _l -> Error "wire-fee already setup"
+    | [ vv ] -> (
+        match v.master_sig_wire = vv.sig_ with
+        | false ->
+            Error "a different wire-fee was already setup for this time frame"
+        | true ->
+            Logs.info (fun m -> m "an identical wire-fee was already setup");
+            Ok ())
+    | _ ->
+        Error
+          "invalid database state, multiple wire-fee found in database for \
+           this time frame"
 
   let jsont = WireFeeSetupMessage.jsont