JJ: Description from the destination commit:

offline tool: add global-fees cmd

JJ: Description from source commit:
.

src/http_management.ml

@@ -433,13 +433,10 @@ module Global_fees = struct
           purse_timeout;
           master_sig;
         } =
-    (* TODO what is kyc_timeout, kyc_fee ? *)
-    let dummy_amount =
-      Amount.make ~sign:None ~currency:"EUR" ~value:0_L ~fraction:0_l
-      |> Result.get_ok
-    in
+    (* TODO KYC
+       what is kyc_timeout, kyc_fee ? *)
     let kyc_timeout = None in
-    let kyc_fee = dummy_amount in
+    let kyc_fee = Amount.dummy_value in
     (* * *)
     let open Bin_sig.GlobalFees in
     verify_f ~f:Sm.verify_with_master_key master_sig
@@ -465,12 +462,28 @@ module Global_fees = struct
     in
     match global_fees with
     | [] ->
-        let+ () = Pg.insert_global_fee db_conn v |> unwrap_err_caqti in
+        let+ () = Pg.insert_global_fees db_conn v |> unwrap_err_caqti in
+        Logs.info (fun m -> m "added global fees");
         ()
-    | _l -> Error "global-fees already setup"
+    | [ vv ] -> (
+        match v.master_sig = vv.master_sig with
+        | false ->
+            Error
+              "a different global-fees was already setup for this time frame"
+        | true ->
+            Logs.info (fun m -> m "an identical global-fees was already setup");
+            Ok ())
+    | _ ->
+        Error
+          "invalid database state, multiple global-fees found in database for \
+           this time frame"
 
   let jsont = GlobalFees.jsont
 
+  (* TODO global_fees
+     ensure it is defined for the current time.
+     there should be only one global_fees for each moment in time
+     and once set for a timeframe, it should not change. *)
   let f req server _env =
     Logs.info (fun m -> m "POST /management/global-fees/");
     let sm = Vif.Server.device Devices.secmod server in