feat(Datastream): Add SQL Server (MSSQL) source support

[pabloqc]

Summary

• Add full SQL Server CDC support to the Datastream-to-BigQuery pipeline, resolving the Source Connection Profile Type Not Supported error when using SQL Server as a Datastream source
• Add SQL Server branch in the Avro format processing path (FormatDatastreamRecordToJson) for correct metadata extraction (_metadata_schema, _metadata_lsn, _metadata_tx_id)
• Add SQL Server sort key definitions (_metadata_timestamp, _metadata_lsn) used by BigQuery MERGE operations
• Add SQL Server schema discovery via the Datastream API (DataStreamClient), including table/column discovery, primary key extraction, and SQL Server-to-BigQuery type conversion
• Add _metadata_lsn to BigQuery default staging table schema
• Update template documentation to list SQL Server as a supported source

Test plan

• Added testSqlServerSortFields in DatastreamRowTest — verifies sort keys are ["_metadata_timestamp", "_metadata_lsn"]
• Added testProcessElement_sqlServer in FormatDatastreamJsonToJsonTest — verifies JSON format processing produces correct SQL Server metadata fields
• All 7 tests pass (mvn test -pl v2/datastream-common)
• Compilation succeeds across all affected modules (mvn compile -pl v2/datastream-common,v2/common,v2/datastream-to-bigquery -am)

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[gemini-code-assist]

Summary of Changes

Hello @pabloqc, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly enhances the Datastream-to-BigQuery pipeline by integrating comprehensive support for SQL Server as a source database. It enables seamless data replication and change data capture from SQL Server instances to BigQuery, ensuring proper schema discovery, metadata handling, and data type conversions. This expansion broadens the utility of the pipeline for users relying on SQL Server for their data warehousing needs.

Highlights

• SQL Server CDC Support: Full SQL Server Change Data Capture (CDC) support has been added to the Datastream-to-BigQuery pipeline, resolving the 'Source Connection Profile Type Not Supported' error.
• Metadata Extraction: SQL Server specific metadata fields such as _metadata_schema, _metadata_lsn, and _metadata_tx_id are now correctly extracted during Avro format processing.
• Sort Key Definitions: Sort key definitions (_metadata_timestamp, _metadata_lsn) for SQL Server have been added to facilitate BigQuery MERGE operations.
• Schema Discovery: The Datastream API (DataStreamClient) now supports SQL Server schema discovery, including table/column identification, primary key extraction, and SQL Server-to-BigQuery type conversion.
• BigQuery Schema Update: The _metadata_lsn field has been added to the default BigQuery staging table schema.
• Documentation Update: Template documentation has been updated to list SQL Server as a newly supported source.

Changelog

• v2/common/src/main/java/com/google/cloud/teleport/v2/cdc/mappers/BigQueryDefaultSchemas.java
  • Added _metadata_lsn field to the default BigQuery schema for PostgreSQL and SQL Server.
• v2/datastream-common/src/main/java/com/google/cloud/teleport/v2/datastream/transforms/FormatDatastreamRecordToJson.java
  • Implemented SQL Server specific metadata extraction for _metadata_schema, _metadata_lsn, and _metadata_tx_id.
• v2/datastream-common/src/main/java/com/google/cloud/teleport/v2/datastream/utils/DataStreamClient.java
  • Imported SQL Server model classes.
  • Extended schema discovery logic to include SQL Server.
  • Added methods for retrieving SQL Server primary keys.
  • Implemented SQL Server to BigQuery data type conversion.
• v2/datastream-common/src/main/java/com/google/cloud/teleport/v2/datastream/values/DatastreamRow.java
  • Configured _metadata_timestamp and _metadata_lsn as sort fields for SQL Server source types.
• v2/datastream-common/src/test/java/com/google/cloud/teleport/v2/datastream/transforms/FormatDatastreamJsonToJsonTest.java
  • Added example SQL Server JSON data.
  • Introduced a new test method testProcessElement_sqlServer to verify SQL Server JSON record processing.
• v2/datastream-common/src/test/java/com/google/cloud/teleport/v2/datastream/values/DatastreamRowTest.java
  • Added testSqlServerSortFields to verify the correct sort fields are returned for SQL Server.
• v2/datastream-to-bigquery/src/main/java/com/google/cloud/teleport/v2/templates/DataStreamToBigQuery.java
  • Updated template documentation to include SQL Server as a supported source database.
  • Modified help text for datastreamSourceType to include 'sqlserver' as a valid override value.

Activity

• The author added testSqlServerSortFields in DatastreamRowTest to verify SQL Server sort keys.
• The author added testProcessElement_sqlServer in FormatDatastreamJsonToJsonTest to verify SQL Server JSON format processing.
• All 7 existing tests passed successfully.
• Compilation succeeded across all affected modules (v2/datastream-common, v2/common, v2/datastream-to-bigquery).

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