We've updated the icons for both MS Teams and Discord in our CDN to

better fit into the rounded avatars in the messages. This change updates

the assets timestamp to force use of the new images and to specify the

path for the new MS Teams assets.
In order to properly leverage the assets timestamp and base URL for the

logo and trophies without having to overwrite all the attributes, we now

define logo_url and trophy_urls as cached properties instead of

attributes. This allows them to be computed dynamically based on any

overridden asset timestamp/base URLs defined by subclasses.

Tested the new download assets and generated URLs.
This will require some testing in production.