The web interface allows working with the file system cluster using
basic HTTP requests. There are many ways to interface with a file system
using HTTP (like WebDAV), but for the firsts versions of ToastyFS I
opted for some custom minimal semantics. Here are they.

GET
    If the path refers to a directory, the listing of its direct children
    is returned as a newline-separated list of relative paths. Children
    that are directories have ending slashes, while files don't:

        image.jpg
        Documents/
        notes.txt

    If the path refers to a file, its contents are returned. Note that
    Range requests are not supported.

    Returns 200 on success, 404 if the file/directory doesn't exist, else 5xx.

HEAD
    Works like GET but doesn't return the content (The Content-Length is
    set as if the payload was being send).

PUT
    The server considers the resource being uploaded as a directory if the
    path ends with a slash, and as a file otherwise:

        photos/     directory
        image.jpg   file

    If the path refers to a directory and no file/directory exists at that
    path, a new one is created and status 201 is returned. If a directory
    existd already, statis 204 is returned. If a file existed already status
    ??? (TODO) is returned. If the payload the request is not empty, the
    operation fails with code 400.

    If the path refers to a file, it creates that file with the specified
    contents. If a file or directory already existed at that path, it is
    overwritten unless the header "X-ToastyFS-Overwrite: no" is sent.
    (TODO error codes)

DELETE
    Deletes the given file or directory. Returns 204 on success, 404 if
    no file or directory existed at that path, else returns 5xx.

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cases:
    PUT file / unused path -> OK
    PUT file / file exists -> overwrite?
    PUT file / directory exists
    PUT directory / unused path -> OK
    PUT directory / file exists
    PUT directory / directory exists

Idea: Use patch on the parent directory to rename
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