[PECOBLR-676] passing session params in open session request instead of SET commands

[sreekanth-db]

Description

This PR refactors session parameter handling in the Go SQL Connector to align with other Databricks drivers (Java, Python). Previously, session parameters were set using SET statements after connection establishment, which was inefficient and inconsistent with other drivers. This new implementation also supports usage of QUERY_TAGS session parameter. Query Tags allow users to attach key-value pairs to SQL executions that appear in the system.query.history table.

Changes Made:

1. Refactored Session Parameter Flow (connector.go):

   • Before: Session parameters were sent via SET statements after OpenSession
   • After: Session parameters are passed directly to TOpenSessionReq.Configuration during session creation
   • Benefit: Aligns with Java and Python drivers, and improves performance

2. Created Example (examples/query_tags/main.go):

   • Demonstrates the usage of Query Tags

3. Enhanced Unit Tests (internal/config/config_test.go):

   • Added QUERY_TAGS to DSN parsing test to verify parameter extraction

Change from User Perspective:

The key difference is in error timing: Previously, invalid session parameters would fail during connection establishment (SET command execution), but now they fail during the first query execution. This happens because the Databricks backend uses lazy validation - it accepts session parameters during connection but validates them only when the first query is executed. This matches Python driver behavior.

Query tags usage example:

connector, err := dbsql.NewConnector(
    dbsql.WithSessionParams(map[string]string{
        "timezone":   "America/Sao_Paulo",
        "ansi_mode":  "true",
        "QUERY_TAGS": "team:engineering",
    }),
)

How is this tested?

• Unit tests
• Manually

Testing Details:

Unit Tests:

• Enhanced DSN parsing tests to verify session parameter extraction for query tags
• All existing tests pass with the new implementation

Manual Testing:

• Verified session parameters including query tags work correctly with real backend using the created example