The type for a JSON document that is stored in a databaseSignature:
It must have an '_id' key that shows the unique identifier of a document
_id allows Unicode characters except for OS reserved filenames and the following characters: < > : " | ? * ¥0.
_id and a filename are linked. So _id is better to be ASCII characters and a case-insensitive name for cross-platform.
_id cannot start or end with a slash.
_id can include paths separated by slashes.
A directory name in paths cannot end with a period or a white space.
A directory name in paths does not allow '.' and '..'.