fix: Properly work with non-numeric version ids

[juliusknorr]

Summary

When using https://github.com/nextcloud/files_versions_s3 version ids in Nextcloud may not be numberic, but:

Version IDs are Unicode, UTF-8 encoded, URL-ready, opaque strings that are no more than 1,024 bytes long.

This PR changes the database schema of richdocuments to make it work with that and adapts code where we enforce numeric values

To test with minio and primary object storage:

docker compose exec minio mc alias set docker http://localhost:9000 nextcloud nextcloud
docker compose exec minio mc version enable docker/nc-nextcloud