fix(mssql): replace permission-based RDS detection with server name analysis

[sgomezvillamor]

Summary

• Add optional is_aws_rds configuration flag to explicitly specify environment type
• Replace unreliable permission-based RDS detection with server name analysis using SELECT @@servername
• Implement comprehensive logging for detection decisions

Problem

The existing RDS detection mechanism was flawed because it relied on permission checks rather than actual environment detection:

Permission-based, not environment-based: The ability to query msdb.dbo.sysjobs depends on user permissions, not the environment type. A restricted user on on-premises SQL Server would also fail this check.

False positives: On-premises SQL Server with:

• Non-sysadmin users
• Restricted database permissions
• Security policies blocking msdb access

Would all incorrectly appear as "RDS"

False negatives: An RDS user with appropriate permissions might actually succeed in querying system objects

Solution

1. Optional explicit configuration: Added is_aws_rds boolean flag that takes precedence when provided
2. Server name detection: Uses SELECT @@servername to check for AWS indicators: amazon, amzn, amaz, ec2, rds.amazonaws.com
3. Robust error handling: Falls back to assuming non-RDS if detection fails
4. Comprehensive logging: Info-level logging for final decisions, debug/warning for intermediate steps

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 45.23810% with 23 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...n/src/datahub/ingestion/source/sql/mssql/source.py	45.23%	23 Missing ⚠️

❌ Your patch check has failed because the patch coverage (45.23%) is below the target coverage (75.00%). You can increase the patch coverage or adjust the target coverage.

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