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/check-json-null-before-converting-values.bad.al

@@ -0,0 +1,11 @@
+codeunit 50173 "Contact Payload Reader Bad"
+{
+    procedure ApplyPayload(var Contact: Record Contact; Payload: JsonObject)
+    var
+        Token: JsonToken;
+    begin
+        if Payload.Get('email', Token) then
+            Contact.Validate("E-Mail", CopyStr(Token.AsValue().AsText(), 1, MaxStrLen(Contact."E-Mail")));
+        Contact.Modify(true);
+    end;
+}