Problem
Students may want to unlink a discord account and link another one.
Solution
Create a resolver that once called unlinks the discord account by setting the discordId, discordRefreshToken, discordAccessToken, and discordAccessTokenExpires to null.
For connivence, we don't want the students to clear a value from local storage in order for the connect-to-discord modal to appear. Add a button in the user profile page that once clicked unlinks the discord account. If no account is linked, it'll show Connect to discord.