A very simple datapack that heals 2 hearts of damage if you sleep the night away.
Simply sleep in your bed till the night passes and you will be healed 2 hearts when you get up.
This hasn't been tested in multiplayer so I'm sure it has a slight "bug" that you still get healed if you stayed in bed long enough for it to count but still not pass night since everyone wasn't in bed. (currently unsure how to get around that)
This datapack was made with the thought of the "naturalRegeneration" setting being turned off to give those who want the challenge of no natural regeneration but don't want to wait for potions or golden apples or any other healing mechanic.