The ID of the document that was updated.
The path to the key in the document that was updated.
The update result's type.
The associated value with different meaning depending on the type:
set, it's the new value at the key path.inserted, it's the new value that was inserted into the array at
index encoded into key path.pushed, it's the new value that was inserted into the array at
key path.popped, it's the value that was popped off the array the
key path.All other types of update results do not have this property set.
The associated amount, only set if type is
incremented.