Brand attributes to write. Every field is optional on update and only the
fields you send are changed — send an explicit null to unset one. name
is required when creating a brand.

The writable field names match the ones a brand is read back with, so an
edit can reuse the values from a GET. The read-only fields (id,
is_default, created, updated) are not accepted here and must be
dropped from a body built that way.

Colors accept three-character hex shorthand and store the expanded
six-character form, so #abc is read back as #aabbcc.

Logos cannot be uploaded through the API. page_logo.url and
player_logo.url must be Wistia delivery URLs
(https://embed-ssl.wistia.com/deliveries/<id>.png) for images already in
the account — for example a URL returned by a previous request to this
endpoint. Any other URL is rejected, because the brand is applied by
resolving that image out of Wistia's own storage. To add a new logo image,
upload it in the Wistia app first.