Missing handling for copy with childs - deepCopy

[baumannsven]

@discordier
Habe in Avisota das dieses programmiert.
avisota/contao-core@d22220d

Angewendet habe ich es hier.
https://github.com/avisota/contao-message/blob/develop/contao/dca/orm_avisota_message.php#L152-L158

Wenn das i.O. ist zumindest der Anfang, würde ich das in den dc-general alls feature branch zur Verfügung stellen.

[discordier]

We will need to discuss this.
As we already discussed briefly on mumble, there is a lot missing here.

I am awaiting your WIP PR with changes which we will then evaluate.
//cc @dmolineus, @stefanheimes

[stefanheimes]

Could be difficult, with the "parent <> child <> child <> child". This can be a huge list of children.

[zonky2]

related #446 and #249

[baumannsven]

What should be do by properties has follow settings:

• do not copy
• unique values