set CAP signature check based on env variable

[maaikelimper]

set CAP signature check based on env variable

#823

[tomkralidis]

Environment variables are not typechecked. Suggest the following:

1. add in wis2box-management/wis2box/util.py:

def str2bool(value: Union[bool, str]) -> bool:
    """
    helper function to return Python boolean
    type (source: https://stackoverflow.com/a/715468)

    :param value: value to be evaluated

    :returns: `bool` of whether the value is boolean-ish
    """

    value2 = False

    if isinstance(value, bool):
        value2 = value
    else:
        value2 = value.lower() in ('yes', 'true', 't', '1', 'on')

    return value2

2. back in wis2box-management/wis2box/data/cap_message.py, update with:

from wis2box.util import str2bool

Then:

check_cap_signature = str2bool(os.getenv('CHECK_CAP_SIGNATURE', False))