Automatic task assignment

Potato can automatically assign instances to annotators based on figurations.

  "automatic_assignment": {
  "on": True, #whether do automatic task assignment for annotators, default False.
  "output_filename": 'task_assignment.json',
  "sampling_strategy": 'random', #currently we support random assignment or ordered assignment. Use 'random' for random assignment and 'ordered' for ordered assignment
  "labels_per_instance": 3,  #the number of labels for each instance
  "instance_per_annotator": 5, #the total amount of instances to be assigned to each annotator
  "test_question_per_annotator": 0, # the number of attention test question to be inserted into the annotation queue. you must set up the test question in surveyflow to use this function

  "users": [  ],
},