How to: upload rules
set upload rules using volflags,  some examples:

* `:c,sz=1k-3m` sets allowed filesize between 1 KiB and 3 MiB inclusive (suffixes: `b`, `k`, `m`, `g`)
* `:c,df=4g` block uploads if there would be less than 4 GiB free disk space afterwards
* `:c,vmaxb=1g` block uploads if total volume size would exceed 1 GiB afterwards
* `:c,vmaxn=4k` block uploads if volume would contain more than 4096 files afterwards
* `:c,nosub` disallow uploading into subdirectories; goes well with `rotn` and `rotf`:
* `:c,rotn=1000,2` moves uploads into subfolders, up to 1000 files in each folder before making a new one, two levels deep (must be at least 1)
* `:c,rotf=%Y/%m/%d/%H` enforces files to be uploaded into a structure of subfolders according to that date format
  * `:c,rotf_tz=Europe/Oslo` sets the timezone (default is UTC unless global-option `rotf-tz` is changed)
  * if someone uploads to `/foo/bar` the path would be rewritten to `/foo/bar/2021/08/06/23` for example
  * but the actual value is not verified, just the structure, so the uploader can choose any values which conform to the format string
    * just to avoid additional complexity in up2k which is enough of a mess already
* `:c,lifetime=300` delete uploaded files when they become 5 minutes old

you can also set transaction limits which apply per-IP and per-volume, but these assume `-j 1` (default) otherwise the limits will be messed up, for example `-j 4` would allow anywhere between 1x and 4x the limits you set depending on which processing node the client gets routed to

* `:c,maxn=250,3600` allows 250 files over 1 hour from each IP (tracked per-volume)
* `:c,maxb=1g,300` allows 1 GiB total over 5 minutes from each IP (tracked per-volume)

notes:
* `vmaxb` and `vmaxn` requires either the `e2ds` volflag or `-e2dsa` global-option

config file example:

```yaml
[/inc]
  /mnt/nas/uploads
  accs:
    w: *    # anyone can upload here
    rw: ed  # only user "ed" can read-write
  flags:
    e2ds       # filesystem indexing is required for many of these:
    sz: 1k-3m  # accept upload only if filesize in this range
    df: 4g     # free disk space cannot go lower than this
    vmaxb: 1g  # volume can never exceed 1 GiB
    vmaxn: 4k  # ...or 4000 files, whichever comes first
    nosub      # must upload to toplevel folder
    lifetime: 300   # uploads are deleted after 5min
    maxn: 250,3600  # each IP can upload 250 files in 1 hour
    maxb: 1g,300    # each IP can upload 1 GiB over 5 minutes
```