Improve implementation of database path relative translations

[apetkau]

Right now, in order to support moving projects/packaging them up to send to other people, I implemented a very basic method to translate absolute to relative paths when storing files in the database. However, this makes use of a global variable to store the path translator:

genomics-data-index/genomics_data_index/storage/model/db/__init__.py

Line 25 in e248ff9

database_path_translator: Optional[DatabasePathTranslator] = None

I don't think this is the best implementation method and would like to explore better options later on.