test(gorm-pg): Add comprehensive tests for PostgreSQL full-text searc…

[w20k]

GORM Raw SQL Method Incorrectly Handles PostgreSQL Full-Text Search Operators

PostgreSQL full-text search operator @@ is not supported in GORM Raw SQL queries with parameterized values due to incorrect parameter binding detection.

// This query contains the @@ operator in the SELECT clause
		err := DB.Raw(`
			SELECT id, name, 
			       to_tsvector('english', name) @@ plainto_tsquery('english', $1) as matches
			FROM users
		`, searchTerm).Scan(&results).Error

Link: go-gorm/gorm#7481