Add an alternative way to provide parameters to command-line slapos request, as a JSON file:

slapos request --parameters-file some-parameters.json

This would be mutually exclusive with the existing --parameters option.

The JSON file is merely loaded into a Python dict that is passed as the partition_parameter_kw argument to slap.OpenOrder.request method.

In comparison the --parameters option builds a Python dict from key=value pairs given on the command-line, and then passes it to slap.OpenOrder.request in exactly the same way.

The --parameters option has the limitation that values can only be strings (i.e. the dict is "flat"), whereas --parameters-file overcomes that limitation, allowing arbitrarily nested list or dict values. Note that this is just a limitation of the command-line interface, the underlying slap.OpenOrder.request accepts any Python dictionnary.