closes https://github.com/TryGhost/Team/issues/1150
Our override of the base Bookshelf `insert` operation so that our own `formatOnWrite()` method is called on attributes was working on a false assumption that an `attrs` attribute is passed in as it is for the `update` operation. Instead Bookshelf's base update uses the `model.attributes` values to create an `attrs` object that is then passed through the usual `.format()` method meaning that our `insert` override was not actually doing anything.
- added a failing regression test for the `formatOnWrite()` override behaviour
- adjusted our insert/update overrides to set an internal `_isWriting` property on the model, then if that property is true our `.format()` override (which is called by Bookshelf on a generated `attrs` object during inserts) we manually call our `.formatOnWrite()` method
- updated both overrides even though `update` was working for consistency and less cognitive overhead for reasoning between two different approaches
no issue
- `formatOnWrite` doesn't override anything in Bookshelf but we use it
within the `override` plugin and sub-models may override it, so it's
easier to keep these things together