Resolve "Refactor database module"

Description

• Added `GenericRepository to handle generic CRUD and query operations.
• Added GenericEntityRepository to handle generic save, getanddelete` operations for a repository that handles a single entity in a table.
• Added repositories for each database models.

Checklist

• I have update updated the @version string in main.go. See https://semver.org/
• I have update CHANGELOG.md with a short description of changes.
• I have run swag init to update the swagger docs.

Marks #206 'done'