Allow uploads without authorization event

[0xtrr]

Authorization events was previously required for uploads but this has recently been updated to be optional.

• Config file must be updated with a new field require_auth under the "upload" section, similar to what we already have for the "get" section.
• The new line in the config should by default be set to true.
• Upload handler must be updated to check the new setting and only validate the auth event if the setting is set to true.

[0xtrr]

This will require some bigger changes in the codebase as well as in the database schema. I'm not sure we want to do this unless people actually need it. That said, it might be better to do this as early as possible to not have to deal with this later on.