v0.0.0-alpha: Internal/data migration (#7)

* get data from database as json

* insert json data into database by API

* eperson and group migration working

* group import

* bitstreamformatregistry, metadatafieldrepository, metadataschemaregistry, registrationdata, eperson, group

* still in progress

* refactoring

* data migration: handle, metadatavalue,group2group

* group2eperson migration

* update import group, import community, comm2comm

* community2community errors

* community errors

* community, community2community work

* collection, collection2community

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Co-authored-by: Michaela Paurikova <[email protected]>