Change MaxConns default from 25 to 4 to match pgxpool defaults.
This ensures consistent behavior between DATABASE_URI and config
file modes, and removes the warning log when using URI mode.
Defaults now reference: https://pkg.go.dev/github.com/jackc/pgx/v5/pgxpool#Config
Add support for PostgreSQL connection URIs via DATABASE_URI env var.
When set, it takes precedence over config files and PoolOptions are
ignored (pool settings can be specified in URI query string).
Add PostgreSQL support to database package alongside existing MySQL support.
Both databases share common infrastructure (pool management, metrics,
transactions) while using database-specific connectors.
database/ changes:
- Add PostgresConfig struct and PostgreSQL connector using pgx/stdlib
- Change MySQL config from DBConfig to *MySQLConfig (pointer)
- Add Config.Validate() to prevent multiple database configs
- Add PostgreSQL connector with secure config building (no password in DSN)
- Add field validation and secure defaults (SSLMode="prefer")
- Support legacy flat PostgreSQL config format for backward compatibility
- Add tests for PostgreSQL configs and validation
New database/pgdb/ package:
- Native pgx connection pool support (*pgxpool.Pool)
- OpenPool() and OpenPoolWithConfigFile() APIs
- CreatePoolConfig() for secure config conversion
- PoolOptions for fine-grained pool control
- Full test coverage and documentation
Security:
- Passwords never exposed in DSN strings
- Set passwords separately in pgx config objects
- Validate all configuration before connection
Architecture:
- Shared code in database/ for both MySQL and PostgreSQL (sql.DB)
- database/pgdb/ for PostgreSQL-specific native pool support
