Handling linked fields

[ammsalme]

Merge should be configurable to handle linked (translitteration) fields correctly: ie. if a normal field and 880 field are linked together with subfield $6, the linked 880 field should be taken to preferred record only if the linked normal field is taken.

[ghost]

Do we only need automatic copying for 880 fields when the normal fields are copied or should we also support rules that operate on 880-fields, e.g:

{
  "fields": [
    "880": {
      "action": "copy"
    }
  ]
}