message: Use field caption as overlay label
diff: {{#overlay-marks group="cardstack-fields" as |mark|}}
  {{#create-overlay at=mark
  - label=(cs-humanize mark.model.name)
  + label=mark.model.caption
  highlighted=(eq mark.id tools.highlightedFieldId)
  hoverable=tools.editing
  class="cs-field-overlay"
  