feat: implement set-based invoice payment calculations and enhance email logging configuration

Fuchs_Database/dbo/Functions/fds_wgd_lastEmails.sql

@@ -2,6 +2,10 @@
 returns table
 as return
 
+-- [config] is NOT NULL but a logging path may have stored '' (or otherwise non-JSON text).
+-- OPENJSON/JSON_QUERY raise on that and took the whole widget down, so the JSON is normalised
+-- once (invalid -> '{}') before anything parses it; a WHERE ISJSON() alone is not guaranteed to
+-- be evaluated ahead of the CROSS APPLY.
 SELECT TOP (@count) 
     [Betreff] = oj.[subject],
     [Empfänger] = (SELECT STRING_AGG(
@@ -9,9 +13,10 @@ SELECT TOP (@count)
              THEN SUBSTRING([value], CHARINDEX('<', [value]) + 1, CHARINDEX('>', [value]) - CHARINDEX('<', [value]) - 1)
              ELSE [value]
         END, ', ')
-     FROM OPENJSON(JSON_QUERY(el.[config], '$.to'))),
-    [attachments] = (SELECT STRING_AGG([value], ', ') FROM OPENJSON(JSON_QUERY(el.[config], '$.attachments'))),
+     FROM OPENJSON(JSON_QUERY(j.[cfg], '$.to'))),
+    [attachments] = (SELECT STRING_AGG([value], ', ') FROM OPENJSON(JSON_QUERY(j.[cfg], '$.attachments'))),
     [gesendet] = FORMAT(el.DateSent, 'dd.MM.yy', 'de-DE')
   FROM [dbo].[fds__emaillog] as el
-    CROSS APPLY OPENJSON(el.[config], '$') WITH ( [subject] nvarchar(255) '$.subject' ) as oj
+    CROSS APPLY (SELECT [cfg] = IIF(ISJSON(el.[config]) = 1, el.[config], N'{}')) as j
+    CROSS APPLY OPENJSON(j.[cfg], '$') WITH ( [subject] nvarchar(255) '$.subject' ) as oj
   order by [DateSent] desc