Limitation of GoogleDrive Android API: no API for copy and share, only one scope is allowed(app-file scope)
Sync with private GoogleDrive storage is now done by GoogleDrive Android API
Custom property is used to store metadata instead of fullText
Metadata JSON file is not uploaded as a file explicitly but stored in each recording's custom property. The JSON file is created when downloaded using the GoogleDrive's custom property.
( recording.wav, metadata.json <-> recording.wav(with meta) in GoogleDrive)
Tagging the uploaded recording can now be reflected in GoogleDrive by changing the custom property
562, #565