Allow DataModel.migrateData to be called recursively for models which are not direct children of the root model schema.

[Fyorl]

Implemented Solution

Data model migration (via the DataModel.migrateData method) is now fully recursive allowing for models which are not direct descendants of the root DataModel to also be migrated.

Example Usage

fields = foundry.data.fields;

class InnerModel extends foundry.abstract.DataModel {
  static defineSchema() {
    return {
      foo: new fields.StringField()
    }
  }

  static migrateData(data) {
    data.foo = "baz";
  }
}

class OuterModel extends foundry.abstract.DataModel {
  static defineSchema() {
    return {
      inner: new fields.ArrayField(new fields.EmbeddedDataField(InnerModel))
    }
  }
}

om = new OuterModel({inner: [{foo: "bar"}]})
om.inner[0].foo; // baz

Original Report

Originally reported by Mana#4176 https://discord.com/channels/170995199584108546/956306859491471420/1065042256559624202

ALL MODULES DISABLED? true
OS, Hosting, Browser (if applicable): any
Short Description of bug: DataModel#migrateData() is not run for EmbeddedDataField contents.
Simple steps to reproduce the bug:
Implement DataModel with noisy migrateData in EmbeddedDataField.
You'll notice the migrateData is never run.

Update: This may be a problem only when the EmbededDataField is inside another data field, like ArrayField or SchemaField.
Update 2: Minimal example fails to reproduce the issue (when used in dev tools console without hooking into system models).

[mkahvi]

Here's some work in progress stuff that this was noticed with...

Starting point is an item model referring to another datamodel in array field:

actions: new fields.ArrayField(new fields.EmbeddedDataField(ActionModel), { required: false }),

Ref: https://gitlab.com/mkahvi/foundryvtt-pathfinder1/-/blob/54c14b0627663ce6b1f488bccaa76f5264f79147/module/data-model/item/consumable-model.mjs#L42

That datamodel then has schemafield for another datamodel:

      damage: new fields.SchemaField(
        {
          parts: new fields.ArrayField(new fields.EmbeddedDataField(DamageModel), { required: false }),
          critParts: new fields.ArrayField(new fields.EmbeddedDataField(DamageModel), { required: false }),
          nonCritParts: new fields.ArrayField(new fields.EmbeddedDataField(DamageModel), { required: false }),
        },
        { required: false }
      ),

Ref: https://gitlab.com/mkahvi/foundryvtt-pathfinder1/-/blob/54c14b0627663ce6b1f488bccaa76f5264f79147/module/data-model/common/action-model.mjs#L87-94

Which then refers to DamageModel:
Ref: https://gitlab.com/mkahvi/foundryvtt-pathfinder1/-/blob/datamodel/module/data-model/common/damage-model.mjs

Adding migrateData to the DamageModel with console logging, that logging never fired. It did not in fact even trigger if the actionmodel had the migrateData.

However recreating all this in minimal datamodel and experimenting in dev tools console alone did not produce the same results.