Suggestion: Add "Change Service" to start screen

[Metal-Frog]

Steps to reproduce

1. Install app in any browser

Expected behaviour

When you do a fresh install but already have a Sync ID you cannot switch directly to the desired service. So you have to create a new Sync ID first and then you can change the service. That means that the newly created Sync ID is never used anymore. It would be better to be able to change the service already on the start screen.

[nero120]

@Metal-Frog strangely enough I was thinking about this recently! Once major browser support is added I'd like to start adding support for syncing to different web services (such as but not exclusively nextcloud), and would imagine adding a selection dropdown for the service type and service url to the login panel.

So essentially yes the plan is to do this! 😄