[x] persist the username from the last Solid username unless the user explicitly clicks log out.
[x] If a username is available and not signed in, then change the "Sign in" to "Sign in as user name"
[x] Add another section below "Identity provider" called "User name"
[x] Remove all sections under "Your profile" and replace with one that when not using Solid, allows you to set / change your user name. It also allows you to toggle to use Solid which disables being able to change your user name (and will mean that when signed into Solid it will show the user name from Solid)
[x] Make the lower identity provider section conditional on using solid.
Extra
[x] Set the user name to the Solid user name when choosing to use Solid storage.
[x] Ensure there is always a user name, i.e. undefined, "", and whitespace are replaced with an Anonymous user name.
Why (hypothesis)
Will allow them to keep editing content despite working in localStorage and or whilst signed out of Solid
Currently
Description (acceptance criteria)
Add another section below "Identity provider" called "User name"Extra
Why (hypothesis)