Verify valid streams on startup and make sure stream is properly deleted #54
Description
When a stream is deleted it is removed from the object store and metadata. In case of it being an active stream there might be parquet files for it in local directory waiting to be synced or might already be synced just after deletion. This behaviour causes it to be loaded as a stream again because a root level prefix is created on storage by s3 sync.
Possible fixes
- Check for .schema on each stream when loading for metadata
- Clean up code that cleans invalid streams if any