Multiple database server support

[sphildreth]

Right now Roadie has a database requirement of MySQL/MariaDB. To increase adoption we need to support multiple database backends - at least a self-contained version that doesn't require someone to setup a database server. Perhaps to this end LiteDB or even SQLite.

[sphildreth]

I think ideally this would just utilize EF Core and have different providers with just a change to the EF core setup, but I think based on what I read about different limitations of various providers that isn't a realistic option. More like we will have to setup different DBContexts specific for each EF provider and then be able to indicate which implementation to use in configuration.

[sphildreth]

After some research this is not trivial. Since different database servers have dialect differences and different approaches/limitations on data there would have to be individual implementations of IRoadieDbContext for each. Not impossible but not trivial.

[sphildreth]

Now Roadie.Library.Data.Context.Implementation has abstracted database provider specific implementations all inheriting from a common RoadieDBContext. I implemented the initial implementation of MySQL.