[12.x] Add streamableUri function to FilesystemAdapter class

[mateuszanella]

Description

This PR adds two new methods to the Illuminate/Filesystem/FilesystemAdapter.php class.

Theese methods are intended to offer a way for developers to set a default PHP stream wrapper prefix in the filesystem configuration, and get a proper URI to directly access a file through PHP default file manipulation functions (fopen, file_get_contents, etc).

The reasoning behind this PR is to add a convenient way to integrate Laravel filesystems to external file manipulation libraries that work exclusively with resources.

Usage

A user may define a default stream wrapper in the filesystems.php config file:

's3' => [
    'driver' => 's3',
    'stream_wrapper' => 's3',
    ...
],

Then, through the Storage facade, the user may check if a given filesystem can provide a streamable URI:

Storage::disk('s3')->providesStreamableUris(); // true

For getting the actual path, the user can use the following function:

Storage::disk('s3')->streamableUri('path/to/file'); // "s3://path/to/file"

Conclusion

I am open to feedback on this. The feature has been relevant to my workspace, and I believe it could be a good addition to the framework.

[mateuszanella]

Also, another thing that could be added is an override to both functions on the LocalFilesystemAdapter class to just return the path if no wrapper is provided in the configuration file, since every path in a local filesystem should be streamable. Also open to suggestions on this.

[taylorotwell]

Thanks for your pull request to Laravel!

Unfortunately, I'm going to delay merging this code for now. To preserve our ability to adequately maintain the framework, we need to be very careful regarding the amount of code we include.

If applicable, please consider releasing your code as a package so that the community can still take advantage of your contributions!