Add data handling and test isolation guidance

- add SCM guidance for deriving base quantities through line unit-of-measure validation`n- add security guidance for parameterizing SetFilter with external text`n- add test isolation guidance for resetting per-test state before initialization guards`n- add web-service guidance for JSON null handling and invariant standard format 9`n- route and cover all five rules with paired evaluation fixtures

microsoft/knowledge/web-services/format-exchanged-values-with-standard-format-9.bad.al

@@ -0,0 +1,27 @@
+codeunit 50171 "Exchange Rate Export Bad"
+{
+    procedure SendRate(CurrencyCode: Code[10]; StartingDate: Date; ExchangeRate: Decimal)
+    var
+        Client: HttpClient;
+        Response: HttpResponseMessage;
+        RequestUrl: Text;
+    begin
+        RequestUrl := StrSubstNo(RateUrlTok, CurrencyCode, Format(StartingDate), Format(ExchangeRate));
+        if not Client.Get(RequestUrl, Response) then
+            Error(RequestFailedErr);
+        if not Response.IsSuccessStatusCode() then
+            Error(RateRejectedErr, Response.HttpStatusCode());
+    end;
+
+    procedure ReadRate(RateText: Text) ExchangeRate: Decimal
+    begin
+        if not Evaluate(ExchangeRate, RateText) then
+            Error(InvalidRateErr, RateText);
+    end;
+
+    var
+        RateUrlTok: Label 'https://rates.example.com/rates?currency=%1&date=%2&rate=%3', Locked = true;
+        RequestFailedErr: Label 'The exchange rate service could not be reached.';
+        RateRejectedErr: Label 'The exchange rate service rejected the rate. Status code: %1.', Comment = '%1 = HTTP status code';
+        InvalidRateErr: Label 'The exchange rate %1 is not a valid decimal number.', Comment = '%1 = received value';
+}