Unable to create Snowflake connection file via connections add if we specify config_args attribute

[nj1973]

If I try to add a Snowflake connection with connect-args attribute it fails:

data-validation connections add -c snowflake_p8 Snowflake \
 --user=dvtuserp8 --password="" \
 --account="my-acc" \
 --database="my-db" \
 --connect-args='{"private_key_file": "/home/nobody/dvt/snowflake/rsa_key.p8", "private_key_file_pwd": "my-pass"}'
...
 in do_connect
    connect_args.setdefault("converter_class", _SnowFlakeConverter)
    ^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'str' object has no attribute 'setdefault'

The problem is that --connect-args remains a string value and is not converted to a dict.

We need to cater for this in cli_tools.get_connection_config_from_args(). If we manually create the connection file then things work from there on.

While fixing the issue we should probably add some help to the connections doc regarding connecting to Snowflake using a key file.