File provisioning on file sinks

[MarekPokornyOva]

Is your feature request related to a problem? Please describe.
Definitely not a bug. Rather lack of abstraction/extensibility. I'd like to be able to customize file provisioning.
Particular use-case is: application needs to create log files in specific directory which is protected with specific permissions which launching account doesn't have assigned but application can access it using impersonalization.

Describe the solution you'd like
I suggest to let developers to specify a file provider which would allow to extend core functionality of file creation. Then use it on right places (e.g.

serilog-sinks-file/src/Serilog.Sinks.File/Sinks/File/FileSink.cs

Line 85 in 53280f5

Stream outputStream = _underlyingStream = System.IO.File.Open(path, FileMode.OpenOrCreate, FileAccess.Write, FileShare.Read);

instead of System.IO.File.Open(path, FileMode.OpenOrCreate, FileAccess.Write, FileShare.Read)).

Describe alternatives you've considered
An alternative could be ability to inherit and extend core classes (e.g. FileSink) but from source code and issue comments it seems that's unwanted design.

Additional context

[nblumhardt]

Hi! Thanks for your message.

The FileLifecycleHooks abstract class supports an OnFileOpened hook, and when that was added our intention was to consider an OnFileOpening(path) hook alongside it, which sounds like it could be a reasonable way to support this use case.

A quick look over the way we open the file suggests having the hook (optionally) return a Stream would work reasonably well. Is this what you had in mind?

I should probably add the disclaimer that new features will be fairly slow to get through to RTM packages in this project, so creating a local fork (or consuming a prerelease package) might be necessary while changes make their way through the pipeline.

[MarekPokornyOva]

@nblumhardt,
yes, your solution sounds good and technically it would be the injection point for a custom file provider.

I appretiate the disclaimer and your honest.

Thanks for your effort!