Evaluate sharing tab integration

[smesterheide]

The data layer, ie. currently fetched list of shares cannot be easily shared between multiple apps

• Frontend JS class Share which is the model for shares from OCS backend API could be packaged in common namespace
• After new shares are added via checkbox we need to fetch the shares from the backend which creates an unnecessary delay and also does layout shifting/flickering

Vuex/Redux would be great fix for all these problems