Add Clone, PartialEq, Ser/De traits to Parent/Children

[cBournhonesque]

Objective

• Add missing traits to hierarchy components Parent and Children, which could be useful (it would be useful for me)

[alice-i-cecile]

All of these other than PartialEq and Serialize could be abused to break the hierarchy. Not saying we shouldn't do this, but just pointing it out.

[james7132]

For the reasons listed above, I'm not too keen on deriving these. Serialize/Deserialize is definitely a maybe if this is being driven by an usability need like network serialization, but I've always been a bit skeptical those kinds of use cases for Entity as well. However, Clone is definitely not OK given the possibility of breaking the hierarchy.

[cBournhonesque]

For the reasons listed above, I'm not too keen on deriving these. Serialize/Deserialize is definitely a maybe if this is being driven by an usability need like network serialization, but I've always been a bit skeptical those kinds of use cases for Entity as well. However, Clone is definitely not OK given the possibility of breaking the hierarchy.

Yes exactly, the main use-case is network serialization; I guess I'll resort to making an internal wrapper component for network serialization then, similarly to what replicon does (https://github.com/projectharmonia/bevy_replicon/blob/master/src/parent_sync.rs#L80).

My hope was to avoid this by replicating Parent and Children directly, but maybe that's not even desirable (as replicating both Parent and Children would duplicate the information transmitted over the wire)