Lock weeks for editing

[okms]

• I have searched for existing issues to avoid creating duplicates

TLDR

Certain roles can close weeks for further edit

Description

There are situations where we should be able to close a week for further edit. E.g. after a week has been billed to a customer and the bill has been approved.

Relevant issues

#62
#593

[pzljanb]

Admin should be able to Lock all Confirmed week from being "unconfirmed"
Manager should be able to Lock all Confirmed week of Subordinates from being "unconfirmed"

Admin should be able to remove Lock of all users