write a converter to migrate the records from the old repository into the new repository

[utnapischtim]

In the current repository are some records that have been imported from Pure and enriched by librarians. The used metadata schema is MAB with some improvements. MAB does not could handle all necessary information. This led to new fields were programmed. (connected to #7)

It is not possible to import the records from Pure directly because then the information set by the librarians would be lost.

• identify the mappings [MAB+Custom -> MARC21]
  • 1701 -> 540 https://www.loc.gov/marc/bibliographic/bd540.html
  • 1452 -> 536 https://www.loc.gov/marc/bibliographic/bd536.html
• implement the converter
• test the converter