Nested field_group inherits of parent field_group settings

Edouard, do you want to have a look?

@julien tekrane: I don't get your need here. Your code overwrites the child field group settings by the parent ones. I'm quite sure this is not a behavior we want by default. Could you elaborate a bit on what you are trying to achieve here? Maybe give a specific example.

@duaelfr
For example you have a Pattern Accordion🟦, and a Pattern Accordion item🔷.

🟦Parent (Accordion patern)
- Setting1 : "valueParent"
🔷child item 1 (Accordion_item pattern)
- Setting1 : empty, so th evalue is "valueParent"
🔷child item 2 (Accordion_item pattern)
- Setting1 : "valueChild2", so the value is "valueChild2"

I want to only set a setting in the parent field_group using Accordion🟦 and this setting will be get by child field_group items🔷. Of course the setting should be declared in the accordion_item.ui_patterns.yml file. If it is set in a child item 🔷, it overrides the parent🟦 setting.

@julien tekrane: just to be sure I understand, are we talking about settings as in "ui_patterns_settings" (ie. defined in the pattern) or settings as in field_group settings (ie. group label, group shown when empty, etc.)?

I both case, I'm not sure we want that inheritance to be the default behavior, so *if* it was to be implemented, it should be opt-in.

@pdureau What do you think about this? I believe this kind of inheritance never existed and still don't exist in 2.x, is it?

@duaelfr: I am talking about "ui_patterns_settings" (ie. defined in the .ui_patterns.yml).