Don't want to write this by hand? GodCraft sets minecraft:annotation.open_door for you with a switch.Get GodCraftOverview
minecraft:annotation.open_door is an entity component: it goes in the components object of a custom mob, or in one of its component groups. Tells the pathfinder that this mob can open doors, so it plans paths through them. Navigation must also allow passing doors.
Example
Inside the components object of BP/entities/<name>.json (values are the defaults or placeholders):
BP/entities/<name>.json
{
"minecraft:annotation.open_door": {}
}