Implement user switching in a group

[Isaac Cheng]

Specification

• At the moment, the website just displays all expenses from a generic POV (not specific to any user).
• Account switching would enable things to be displayed specific to the user, so that the most important details are highlighted.
  • For example, we could show 'Outstanding balance' above the list of expenses to show how much the user owes in total.
  • We could also display some text below each member of the group stating how much they owe money to or are owed by that person.