Add account manager

[JonathanMM]

I use a kanboard on many organisation and I wish the possibility to use kandroid with many instance of kanboard (or have an easy way to switch quickly between instance)

[jpellegrini]

I agree that it would be great. I can easily install several instances of Kanboard; it would be good to be able to pick an instance from the app -- It would allow me to isolate contexts.