IssueTracker

Currently there is a function `create_gs_key` (https://cloud.google.com/appengine/docs/python/refdocs/google.appengine.ext.blobstore.blobstore#google.appengine.ext.blobstore.blobstore.create_gs_key), which generates the blob key based on Google Cloud Storage filename given. But in result filename (and other file information, like content-type) is lost from GAE perspective.
When migrating from Files API usage to GCS each and every user has to write additional code to keep filenames (which were early stored as part of BlobInfo). So, migration to GCS is quite painful.

There should be a function to convert blob key back to filename (moreover, sources say that currently it is just base64 encoded). So, we will not have to keep filenames and filetypes separately. Or, alternative approach is to be able to generate and save BlobInfo data by passing additional parameters to `create_gs_key` - such approach will even more simplify the migration.