Change args type, Add test script, Update de-auth.

    - Only the token set by clj-mojo within the namespace can be
      deleted.
    - Changes in arguments type,
        1. offer-create: title, base-price, currency are mandatory and
        positional, while others are optional (but keyword parameters)
        2. offer-edit: slug is mandatory and positional, while others
        are optional (but keyword parameters).
    - Adds test script for unit testing.
    - Minor indentation changes (replaced tabs by spaces).