Largest change is in the FFI crate.
With 2024 (but not 2021) edition unsafe code
inside unsafe functions should be marked separately
so we can mark exactly the code that is unsafe.
Some CFFI functions even have no unsafe code inside.
Most interesting change is that .strdup()
functions are not marked as unsafe anymore.
They are allocating memory and return raw pointers,
but there is nothing unsafe about it.
Only using the returned raw pointers is unsafe.
This way calls to .strdup() don't have to be marked
with unsafe{} blocks.
Add a new crate `deltachat_time` with a fake `struct SystemTimeTools` for mocking
`SystemTime::now()` for test purposes. One still needs to use `std::time::SystemTime` as a struct
representing a system time. I think such a minimalistic approach is ok -- even if somebody uses the
original `SystemTime::now()` instead of the mock by mistake, that could break only tests but not the
program itself. The worst thing that can happen is that tests using `SystemTime::shift()` and
checking messages timestamps f.e. wouldn't catch the corresponding bugs, but now we don't have such
tests at all which is much worse.
