You are really discussing an improvement in programming languages rather than in databases. Innovation in programming languages themselves tend to be in languages like Haskell which give you much more abstraction power. You should take a look at Haskell beam https://haskell-beam.github.io/beam/tutorials/tutorial1/ or Esqueleto https://github.com/bitemyapp/esqueleto and you will find that these libraries achieve much tighter integration between the database and the rest of the language. I'm especially fond of Beam: the way to define data types and tables, the way to write queries just feel incredibly intuitive to me.
> managing the database source in the repository, integrate the database into tests easier
These are much easier problems to solve. Many people have already solved it.
> managing the database source in the repository, integrate the database into tests easier
These are much easier problems to solve. Many people have already solved it.