JSON_OBJECTAGG support for OVER clause

## Description
JSON_OBJECTAGG supports windowed aggregate usage via the OVER (PARTITION BY ...) clause in SQL Server, but ScriptDOM was missing support for parsing and generating it. This PR adds OVER clause support for JSON_OBJECTAGG in the TSql170 parser and script generator.

SQL syntax now supported:
`sql
   SELECT JSON_OBJECTAGG(CustomerName:OrderDate) OVER (PARTITION BY OrderDate) FROM Customers;
   SELECT JSON_OBJECTAGG(CustomerName:OrderDate ABSENT ON NULL) OVER (PARTITION BY OrderDate) FROM Customers;
   SELECT JSON_OBJECTAGG(CustomerName:OrderDate NULL ON NULL) OVER (PARTITION BY OrderDate) FROM Customers;
   SELECT JSON_OBJECTAGG(CustomerName:OrderDate NULL ON NULL RETURNING JSON) OVER (PARTITION BY OrderDate) FROM Customers;
`

## Changes
- Updated JSON_OBJECTAGG production in TSql170.g to optionally parse an OVER clause
- Enhanced SqlScriptGeneratorVisitor.FunctionCall.cs to generate the OVER clause in the output
- Added new baseline and test scripts (JsonObjectAggOverClause170.sql in both Baselines170 and TestScripts)

## Additional Information
No AST changes were needed -- FunctionCall.OverClause already exists in Ast.xml.
The grammar uses overClauseNoOrderBy (not overClause) since, like regular aggregates (e.g., SUM() OVER (...)), the ORDER BY within the OVER clause is not applicable for JSON_OBJECTAGG as a windowed aggregate.
All older parsers (80-160) produce 4 errors each (one per test statement) since the JSON_OBJECTAGG key:value syntax is not recognized pre-TSql170.

Author: ssreerama

SqlScriptDom/Parser/TSql/TSql170.g

@@ -33167,6 +33167,7 @@ jsonObjectBuiltInFunctionCall [FunctionCall vParent]
 
 jsonObjectAggBuiltInFunctionCall [FunctionCall vParent]
 {
+    OverClause vOverClause;
 }
     :   (
             jsonObjectAggExpressionList[vParent]
@@ -33177,6 +33178,12 @@ jsonObjectAggBuiltInFunctionCall [FunctionCall vParent]
         {
             UpdateTokenInfo(vParent, tRParen);
         }
+        (
+            vOverClause=overClauseNoOrderBy
+            {
+                vParent.OverClause = vOverClause;
+            }
+        )?
     ;
 
 jsonQueryBuiltInFunctionCall [FunctionCall vParent]

SqlScriptDom/ScriptDom/SqlServer/ScriptGenerator/SqlScriptGeneratorVisitor.FunctionCall.cs

@@ -70,6 +70,8 @@ public override void ExplicitVisit(FunctionCall node)
                     GenerateSpace();
                 GenerateReturnType(node?.ReturnType);
                 GenerateSymbol(TSqlTokenType.RightParenthesis);
+                // Generate OVER clause for windowed json_objectagg
+                GenerateSpaceAndFragmentIfNotNull(node.OverClause);
             }
             else if (node.FunctionName.Value.ToUpper(CultureInfo.InvariantCulture) == CodeGenerationSupporter.JsonArray)
             {

Test/SqlDom/Baselines170/JsonObjectAggOverClause170.sql

@@ -0,0 +1,11 @@
+SELECT JSON_OBJECTAGG(CustomerName:OrderDate) OVER (PARTITION BY OrderDate)
+FROM Customers;
+
+SELECT JSON_OBJECTAGG(CustomerName:OrderDate ABSENT ON NULL) OVER (PARTITION BY OrderDate)
+FROM Customers;
+
+SELECT JSON_OBJECTAGG(CustomerName:OrderDate NULL ON NULL) OVER (PARTITION BY OrderDate)
+FROM Customers;
+
+SELECT JSON_OBJECTAGG(CustomerName:OrderDate NULL ON NULL RETURNING JSON) OVER (PARTITION BY OrderDate)
+FROM Customers;

Test/SqlDom/Only170SyntaxTests.cs

@@ -21,6 +21,7 @@ public partial class SqlDomTests
             new ParserTest170("AiGenerateChunksTests170.sql", nErrors80: 19, nErrors90: 16, nErrors100: 15, nErrors110: 15, nErrors120: 15, nErrors130: 15, nErrors140: 15, nErrors150: 15, nErrors160: 15),
             new ParserTest170("JsonFunctionTests170.sql", nErrors80: 29, nErrors90: 8, nErrors100: 54, nErrors110: 54, nErrors120: 54, nErrors130: 54, nErrors140: 54, nErrors150: 54, nErrors160: 54),
             new ParserTest170("JsonArrayAggOrderBy170.sql", nErrors80: 10, nErrors90: 9, nErrors100: 9, nErrors110: 9, nErrors120: 9, nErrors130: 9, nErrors140: 9, nErrors150: 9, nErrors160: 9),
+            new ParserTest170("JsonObjectAggOverClause170.sql", nErrors80: 4, nErrors90: 4, nErrors100: 4, nErrors110: 4, nErrors120: 4, nErrors130: 4, nErrors140: 4, nErrors150: 4, nErrors160: 4),
             new ParserTest170("ComplexJsonObjectFunctionTests170.sql"),
             new ParserTest170("AiGenerateEmbeddingsTests170.sql", nErrors80: 14, nErrors90: 11, nErrors100: 11, nErrors110: 11, nErrors120: 11, nErrors130: 11, nErrors140: 11, nErrors150: 11, nErrors160: 11),
             new ParserTest170("CreateExternalModelStatementTests170.sql", nErrors80: 2, nErrors90: 2, nErrors100: 2, nErrors110: 2, nErrors120: 2, nErrors130: 4, nErrors140: 4, nErrors150: 4, nErrors160: 4),

Test/SqlDom/TestScripts/JsonObjectAggOverClause170.sql

@@ -0,0 +1,11 @@
+-- JSON_OBJECTAGG with OVER clause (PARTITION BY)
+SELECT JSON_OBJECTAGG(CustomerName:OrderDate) OVER (PARTITION BY OrderDate) FROM Customers;
+
+-- JSON_OBJECTAGG with ABSENT ON NULL and OVER clause
+SELECT JSON_OBJECTAGG(CustomerName:OrderDate ABSENT ON NULL) OVER (PARTITION BY OrderDate) FROM Customers;
+
+-- JSON_OBJECTAGG with NULL ON NULL and OVER clause
+SELECT JSON_OBJECTAGG(CustomerName:OrderDate NULL ON NULL) OVER (PARTITION BY OrderDate) FROM Customers;
+
+-- JSON_OBJECTAGG with NULL ON NULL, RETURNING JSON, and OVER clause
+SELECT JSON_OBJECTAGG(CustomerName:OrderDate NULL ON NULL RETURNING JSON) OVER (PARTITION BY OrderDate) FROM Customers;