NIFI-14869: Add MSSQL MERGE-based upsert via new DatabaseDialectService

[Adelwageeh96]

Implement supportsUpsert() and getUpsertStatement() in MSSQLDatabaseDialectService to produce a MERGE statement for UPSERT operations on SQL Server.

• Added new controller service: MSSQLDatabaseDialectService Provides SELECT with paging, UPSERT using MERGE, and basic ALTER/CREATE DDL generation for SQL Server 2012+.

• Added new controller service: MSSQL2008DatabaseDialectService Extends MSSQLDatabaseDialectService to support SQL Server 2008, including SELECT with ROW_NUMBER() paging.

• Registered both services in META-INF/services/org.apache.nifi.controller.ControllerService Enables NiFi to discover and use the new MSSQL dialect services.

• Added unit tests:

  • TestMSSQLDatabaseDialectService.java: Verifies SQL generation and UPSERT logic for MSSQLDatabaseDialectService.
  • TestMSSQL2008DatabaseDialectService.java: Verifies paging and SELECT logic for MSSQL2008DatabaseDialectService.

Summary

NIFI-14869

Tracking

Issue Tracking

• Apache NiFi Jira issue created

Pull Request Tracking

• Pull Request title starts with Apache NiFi Jira issue number: NIFI-14869
• Pull Request commit message starts with Apache NiFi Jira issue number: NIFI-14869

Pull Request Formatting

• Pull Request based on current revision of the main branch
• Pull Request refers to a feature branch with one commit containing changes

Verification

Build

• Build completed using ./mvnw clean install -P contrib-check
  • JDK 21

Licensing

• No new dependencies introduced

Documentation

• Documentation formatting appears as expected in rendered files