Export field “Collectors” - Display name

[Muskovit]

Is your feature request related to a problem? Please describe.
The field “Collectors” in Material Samples > Collecting Event > Collecting Agents with agents from the agents module is not included in the export. Thus, we can’t export the standardized collectors' names. Using the field “Verbatim Collectors” instead is too inaccurate. Providing the names of the collectors of a material sample is an important part of publishing our historical collections online.

Describe the solution you'd like
We suggest to add the Display name of “Collectors” into the export.