emptyToken can be  private
MediaProvider: all non-publishable methods -> private (if not, protected)
BugFix: OAuthSession does not take type parameters any more
fixup! MediaProvider: all non-publishable methods -> private (if not, protected)
fixup! fixup! MediaProvider: all non-publishable methods -> private (if not, protected)
MediaProvider: delete ProviderApi class parameter
Rearrange methods
Reorganize exports
BugFix: val: measurementUnit: protected <-private
Remove unneeded type parameter
Add canary for NullPointer
YouTubeMediaProvider: apply fixes from FlickrMediaProvider
Delete unused "invoke_parameterless_method" method
Implement termsOfUseUri, endPointRootUri, maxResultsPerQuery, targetLicenses
fixup! Implement termsOfUseUri, endPointRootUri, maxResultsPerQuery, targetLicenses
All YouTube request are GET