Groups
A group is who a group-scoped event is about. A static group keeps a list you add to; a dynamic group holds whoever's attributes contain its filter, so nobody keeps it up. Beside the groups somebody keeps are temporary lists, picked by a person for one send: you can see them, but a key cannot change one and an event cannot name one. In the Standard lens a group is, for example, “Group A”.
POSTBuild groups from a subject attribute
Requires groups:write. Makes one dynamic group per value the subjects hold for the attribute you name — or one per combination, for up to four — and returns them. Safe after every import: what exists is left exactly as it is, and nothing is tidied away.
200 with the groups those attributes keep up, made now or before. 400 for a key no subject can carry.
A bare JSON array. Each item is one group: the same fields in every pack. Press Response on the sample to see one whole.
On failure the body is { error, code } instead.