Fixed bulk copy for batch inserting null datetime type data when sendTemporalDataTypesAsStringForBulkCopy=false

[muskan124947]

Description

Fixed an issue where inserting null temporal data types (datetime, smalldatetime) would fail when using bulk copy API (useBulkCopyForBatchInsert=true) with sendTemporalDataTypesAsStringForBulkCopy=false.

Background

Extended bulk copy for batch insert support for temporal and money datatypes #2670 - added bulk copy for batch insert support for temporal and money data types.
When sendTemporalDataTypesAsStringForBulkCopy connection property set to true (default), temporal types are sent as varchar strings to work around bulk copy limitations. When set to false, temporal types are sent as their native types.

However, the implementation missed proper null handling when sendTemporalDataTypesAsStringForBulkCopy=false, causing the following error:

java.sql.BatchUpdateException: Data type datetime is not supported in bulk copy. 
at com.microsoft.sqlserver.jdbc.SQLServerPreparedStatement.executeBatch(SQLServerPreparedStatement.java:2259)

Test Coverage

Added comprehensive test cases:

• testBulkInsertWithNullDataForAllTemporalTypesAndMoney() - validates null handling when sendTemporalDataTypesAsStringForBulkCopy=false

• testBulkInsertWithNullDataForAllTemporalTypesAndMoneyAsVarchar() - validates null handling when sendTemporalDataTypesAsStringForBulkCopy=true (default)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 51.61%. Comparing base (87f0553) to head (51997af).

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #2702      +/-   ##
============================================
+ Coverage     51.50%   51.61%   +0.11%     
- Complexity     4050     4087      +37     
============================================
  Files           149      149              
  Lines         34136    34136              
  Branches       5700     5700              
============================================
+ Hits          17581    17620      +39     
- Misses        14076    14078       +2     
+ Partials       2479     2438      -41     

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