Try to decode the content's raw data and fail gracefully
As of today, if the content's raw data is not utf-8, the webapp will fail.
We must trap any decoding error that could happen.
As a fallback, propose the user an example link to pass a request parameter as another encoding to try and use (ascii, etc...).
Also, unconditionally, propose a link to download the content's raw data.
Migrated from T296 (view on Phabricator)