Pallets: review if there is a better way to validate user input

[cernicc]

This issue was created due to the debate here. We debated where should we check if the sectors passed by the users are empty.

The overall issue is how and where to validate user input on the extriniscs. Currently, we are checking things like, does the sector exists for some storage provider on multiple different locations. Where and how should this be handled?

[jmg-duarte]

Code has been working ok, closing to reduce noise in the issue tracker.

A refactor may be in order in the future, but we'll worry about it then.