Apostrophe 4.4.3: improvements to "convert" allowing values that support it to remain empty

[boutell]

The following changes were made in version 4.4.3:

Fixes

• Do not use schema field.def when calling convert. Applying defaults to new documents is the job of newInstance() and similar code. If you wish a field to be mandatory use required: true.
• As a convenience, using POST for pieces and pages with _newInstance: true keeps any additional req.body properties in the API response. This feature unofficially existed before, it is now fully supported.

"What is the effect of this change?" Until this change, field types like color that support being left blank were forced to have their def value again each time the editor was opened again. This was particularly frustrating for color fields in the palette. Now they can be intentionally cleared without being reset to their initial default (def), as long as they are not marked required: true.

"Why was this change released early?" Normally we make new releases on a monthly cadence, however this fix was delayed past our normal monthly window for additional testing. We have decided to release it without waiting for next month's window in order to accommodate the needs of a customer.