file.keyvalue should create the file if it doesn't exist

[TheNetworkIsDown]

If you don't yet have a file that you would like to create by key/value pairs, then this state should just create it.
Or at least be able to do it by using a "create=xxx" option.

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[OrangeDog]

If this feature is added, then file.replace should also get it.

If you are wanting to manage (and create) an entire key-value file, then in 3006 you will be able to use file.serialize with serializer: keyvalue.