I would attempt to make it myself, but looking at tutorial videoes of how to mod showed me that it would take me a very long time to understand, so hopefully someone good at modding will pick up the idea.
The basic idea behind the animal containment is that some recipes, such as a Beebox or Presthatitator, require live animals to make, but they may end up dying in your inventory while trying to collect the other ingredients to the recipie or waiting for your teammates to get back with the ingredients in DST or you don't have the room in your inventory after catching them. So, you could put the animals in the containment while getting the other ingredients.
Of course, the obvious solution is to just get the other ingrdients and then the animals, but I still think it might be useful depending on the circumstances. Plus, it could be used during Winter and Summer to store a large amount of live rabbits which can then be killed and eaten without having to venture out of base and try to catch them
The Containment would be built with a Science Machine in the Structures tab and its ingredients would probably be boards, cut stone, spider silk and maybe something else, it's up to whoever wants to make it, though it would proabably have to be fairly pricey. And it's limits would be maybe 20 animals at any time, can only store one type of animal and the animals inside have to be fed otherwise they die