Yibo He

> @cs1137195420 I'll try to work on it.

@jackleibest The PostgreSQL adapter is not implemented yet, we will implement it later and put it in a separate repository named [postgresql-adapter](https://github.com/casbin-cpp/postgresql-adapter).

@hsluoyz @JalinWang I tested the functions in built_in_functions with Casbin's test cases, and found that some of the original keymatch functions still failed in some examples. I will implement these...

> @cs1137195420 a good practice is using exactly the same logic as Golang, just port Go code to C++. I agree with you. That is exactly what I am going...

> > Without the support for KeyMatch4 and ABAC model in Casbin-cpp , some test cases are missing. > > @cs1137195420 can you add `KeyMatch4()` to unblock Jianning here? Sure,...