Add support for deleting fields from documents

[IjzerenHein]

Currently, deleting fields from a Document is not possible when using schemas. Without schemas it is possible by using firebase.firestore.FieldValue.delete() in the Document.update/set functions, although this is a bit of a cumbersome API.

Proposal API that treats undefined as a special value to delete a field.

doc.update({
  status: undefined // this will delete the field status
});

Additional requirements/info:

• undefined is syntactic sugar for firebase.firestore.FieldValue.delete()
• null, sets the value of the field to null in firestore
• undefined can be used with schemas
• firebase.firestore.FieldValue.delete() should also be supported (however not work with schemas)

[IjzerenHein]

This issue has already been resolved. To delete fields from documents use:

const { getFirebase } from 'firestorter';
doc.update({
  memberCount: getFirebase().firestore.FieldValue.delete()
});