Refactor: the project is now divided into a more clear structure, with **Infrastructure** and **Application** layers added.
Refactor: configurations are split into sections for different layers.
Fix: now EF Core related operations, such as migration, should be invoked in `OptixServe.Infrastructure`, with config file and data dir passed into `dotnet ef` command. See `OptixServe.Infrastructure/Utilites/DesignTimeDbContextFactory.cs` for details.
Fix: EF migrations are ignored in gitignore on purpose in early development.
