Long answer: Discord's API does not allow me to receive the Nitro status of an user. The requested user would have to authorize Discord.ID (Oauth2, like when you add a Bot) in order to get the information.
The Early Supporter badge is shown on discord.id if the user had Nitro before October 10th, 2018.
Will there be a way to track users in a server?
No. This is not supported by Discord and also against a core value of mine: Privacy.
Will there be a way to get details such as Server Logo, Server Icon?
No. Beside some technical impossiblities, it's not what discord.id should be about.
Will there be a way to lookup users by username?
No. This is technically not possible nor supported by Discord.
Yes. Use it and don't try to use discord.id as an API.