feature: import model endpoint

[feekosta]

Description

This PR adds the necessary structure to import model.

Resolves

Resolves #76

How Has This Been Tested?

• call export endpoint and save file

curl --location --request GET 'localhost:3001/models/MODEL_ID/export' \
--header 'x-user-id: USER_ID'

• call import endpoint with file

curl --location --request POST 'localhost:3001/models/import' \
--header 'x-user-id: USER_ID' \
--form 'model=@"/path/to/file"'

• should return the imported model