InstantEntity does not allow dropping undefined keys

[uriva]

e.g. for

type MyType = InstantEntity<typeof db, "someType">;

const introEvent: MyType = {
  field: 123,
  optionalField: undefined,
};

works
but

const introEvent: MyType = {
  field: 123,
};

will be a typing error.

[stopachka]

Hey @uriva -- starting in 0.17.4, optional fields should work! Let me know how it goes.