Brainstorm: Refactor farm animals to have animal groups as separated model

[fedjo]

Create a AnimalGroup entity and connect Parcel <-> Animal Group
Remove connection Parcel from Animal

We need to brainstorm more on how to implement the AnimalGroup feature, which operation will be supported on the group level, if we mange small animals (like pigs,...) only using the group whereas we treat cattles as individual animals...

Feedback from SIP2

A better way to allocate an animal to a parcel would be to it at animal group level.
It is to much tedious and repetitive to do it animal by animal whereas in the reality it is managed group by group
And if an animal goes in or out a parcel (out a group), it needs to modify the group. Doing this supposes to have a specific animal group management module.
That’s the way that the herd management software work.

Please note that all the above remarks deals only with cattle. Other species are managed differently.
The main difference is that small ruminants and pigs are managed by batches whereas the cattle are managed individually.

Note: We need to get more info from SIP2 on how this functionality is supposed to work