Use postgres, mysql or sqlite for backend driver

[javuto]

Implementing #86 and be able to use other backend databases. Now you can use postgres, mysql or sqlite to be specified in the db.json file or parameters.

[Copilot]

Pull Request Overview

This PR implements support for multiple database backends (PostgreSQL, MySQL, and SQLite) as requested in issue #86. Previously, the application only supported PostgreSQL as the backend database.

Key changes:

• Added database type configuration and command-line flags to specify the database backend
• Extended the database configuration structure to support different connection parameters for each database type
• Implemented database driver selection logic in the backend manager

Reviewed Changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 2 comments.

File	Description
pkg/config/flags.go	Added CLI flags for database type selection and SQLite file path configuration
pkg/backend/backend.go	Extended backend manager to support PostgreSQL, MySQL, and SQLite drivers with appropriate connection handling
go.mod	Added MySQL driver dependency to support the new database backend option
deploy/config/db.json	Updated default configuration template to include database type specification

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