Remove the prefix of the google apis and bucket name from the database

[williamatpaper]

Is your feature request related to a problem? Please describe.
When using this plugin, the full URL of the path to the content within the bucket gets stored in the database. We're currently in the middle of migrating between buckets, and upon investigation, we determined that we'd not only need to migrate the content in the bucket, but also update the database to reference the new URL. I believe it's best practice to store the path to the image, and let the app dynamically construct the URL for you.

Describe the solution you'd like
When media gets uploaded, the database holds a relative path to it. When the app needs to load the media, it prepends the prefix based on the baseURL and basePath provided dynamically.

Describe alternatives you've considered
Leaving the URLs in the database, and running a query to update them.