Add type check when creating a new MerginProject

[constantinneagu]

When initializing a new MerginProject, directory must be a str. If we pass something else, like a pathlib.Path, we get a weird error when the logger is initialized.

[MarcelGeo]

Hi @constantinneagu .

I double-checked what is happening here. Wouldn't it be better to just cast logger_name to a string in the setup_logging method? I think it's just an abstract logger name for the logging library.

str(logger_name)

We are using the os library for manipulating paths in the code. Therefore, we can probably use path-like objects in mergin-client.

Thanks for your contribution, @constantinneagu .

[constantinneagu]

Hi @MarcelGeo.

Since I'm not familiar with the code base, I was trying to avoid introducing too many side effects, while at the same time (potentially) sparing a future user from a little bit of frustration. Your solution makes more sense, and it will remove a little bit of weirdness from my side of the code 😄. I'm going to try it and report back.

[MarcelGeo]

If everything is running properly now, thanks for your contribution @constantinneagu