If I scrap a locked safe, does its content go to the workshop?
In Fallout 4, when using the workshop in a settlement you can scrap containers. If you do so while they still contain something their content go to the workshop inventory (according to comments on this answer).
But you can also scrap locked safes. If you do so, does the content also go to the workshop inventory, negating the need to unlock the safe ?
Yes. If you scrap a locked safe the contents of that safe are then transferred to your workshop, negating the need to unlock the safe.