[Release-1.0] Add UI to change username on first sign in

[adilanchian]

If you are signing in with a platform for the first time, we should prompt you to see if you would like to change your username before setting it in stone.

I think some sort of modal could probably do the trick here

[adilanchian]

We actually have begun working on this! This is what we are currently doing for Apple Music and it works great. The next step here is to actually set this up to work with Spotify as well.

[adilanchian]

What We Did Today

• We started looking into how to support changing usernames for Spotify accounts
• We started to setup a NavigationService singleton where we can use the navigation library essentially anywhere
• Realized that we need to do a bit more work on how to check to see if we should prompt the Add Username view
• 120 squats. RIP my legs.

What We Will Do Next Time

• [ ] Finalizing the NavigationService singleton
• [ ] Setup proper handling for checking if we should prompt Add Username flow
• [ ] TEST IT