Update Group Membership

Set the group of one or more experiments (PUT /experiment-groups/membership).

Membership is a single-valued relationship, so assign, bulk assign, move, and remove are all this one call with different values: group_id is the destination group, and null means unassign (the experiments return to the standalone Experiments section). experiment_ids carries one id for the single-card path and several for a multi-select.

How many experiments the membership call actually updated.