Add IUser abstraction

src/Core/Entities/IUser.cs

@@ -0,0 +1,88 @@
+namespace Discord.Core
+{
+    /// <summary>
+    /// An interface representing the collection of operations that can be
+    /// performed on a user.
+    /// </summary>
+    public interface IUser
+    {
+        /// <summary>
+        /// Gets a value indicating the unique identifier for this user.
+        /// </summary>
+        ulong Id { get; }
+
+        /// <summary>
+        /// Gets a value representing the user's username.
+        /// </summary>
+        string Username { get; }
+
+        /// <summary>
+        /// Gets a value representing the user's 4-digit discriminator.
+        /// </summary>
+        short Discriminator { get; }
+
+        /// <summary>
+        /// Gets a value representing the user's avatar hash, or
+        /// <code>null</code> if one is not present.
+        /// </summary>
+        string? AvatarHash { get; }
+
+        /// <summary>
+        /// Gets a value representing whether the user is a bot account, or
+        /// <code>null</code> if it is not known.
+        /// </summary>
+        bool? IsBot { get; }
+
+        /// <summary>
+        /// Gets a value representing whether the user is an Official Discord
+        /// System account, or <code>null</code> if it is not known.
+        /// </summary>
+        bool? IsSystem { get; }
+
+        /// <summary>
+        /// Gets a value representing whether the user has two-factor
+        /// authentication enabled, or <code>null</code> if it is not known.
+        /// </summary>
+        /// <remarks>
+        /// If <see cref="IsBot"/> is true, this field represents the owner's
+        /// two factor authentication status.
+        /// </remarks>
+        bool? HasMfaEnabled { get; }
+
+        /// <summary>
+        /// Gets a value representing the user's locale, or <code>null</code>
+        /// if it is not known.
+        /// </summary>
+        string? Locale { get; }
+
+        /// <summary>
+        /// Gets a value representing whether the user's E-Mail address is
+        /// verified, or <code>null</code> if it is not known.
+        /// </summary>
+        bool? EmailVerified { get; }
+
+        /// <summary>
+        /// Gets a value representing the user's E-Mail address, or
+        /// <code>null</code> if it is not known.
+        /// </summary>
+        string? EMailAddress { get; }
+
+        /// <summary>
+        /// Gets a value representing the flags on the user's account, or
+        /// <code>null</code> if it is not known.
+        /// </summary>
+        UserFlags? Flags { get; }
+
+        /// <summary>
+        /// Gets a value representing the type of nitro subscription on the
+        /// user's account, or <code>null</code> if it is not known.
+        /// </summary>
+        NitroType? NitroType { get; }
+
+        /// <summary>
+        /// Gets a value representing the public flags on the user's account,
+        /// or <code>null</code> if it is not known.
+        /// </summary>
+        UserFlags? PublicFlags { get; }
+    }
+}

src/Core/NitroType.cs

@@ -0,0 +1,21 @@
+namespace Discord.Core
+{
+    /// <summary>
+    /// The type of Nitro subscription which a <see cref="IUser"/> may have.
+    /// </summary>
+    public enum NitroType
+    {
+        /// <summary>
+        /// The user has no nitro subscription.
+        /// </summary>
+        None = 0,
+        /// <summary>
+        /// The user has Nitro Classic.
+        /// </summary>
+        Classic = 1,
+        /// <summary>
+        /// The user has Discord Nitro.
+        /// </summary>
+        Nitro = 2,
+    }
+}

src/Core/UserFlags.cs

@@ -0,0 +1,68 @@
+using System;
+
+namespace Discord.Core
+{
+    /// <summary>
+    /// Flags which may be present on an <see cref="IUser"/>
+    /// </summary>
+    [Flags]
+    public enum UserFlags
+    {
+        /// <summary>
+        /// The user has no flags on their account.
+        /// </summary>
+        None = 0,
+        /// <summary>
+        /// The user is a Discord employee.
+        /// </summary>
+        Employee = 1 << 0,
+        /// <summary>
+        /// The user is a Discord partner.
+        /// </summary>
+        Parnter = 1 << 1,
+        /// <summary>
+        /// The user part of HypeSquad events.
+        /// </summary>
+        HypeSquad = 1 << 2,
+        /// <summary>
+        /// The user has the first level bug hunter badge.
+        /// </summary>
+        BugHunterLevel1 = 1 << 3,
+        /// <summary>
+        /// The user is part of HypeSquad Bravery.
+        /// </summary>
+        HypeSquadBravery = 1 << 6,
+        /// <summary>
+        /// The user is part of HypeSquad Brilliance.
+        /// </summary>
+        HypeSquadBrilliance = 1 << 7,
+        /// <summary>
+        /// The user is part of HypeSquad Balance.
+        /// </summary>
+        HypeSquadBalance = 1 << 8,
+        /// <summary>
+        /// The user is an early discord supporter.
+        /// </summary>
+        EarlySupporter = 1 << 9,
+        /// <summary>
+        /// The user is a team user.
+        /// </summary>
+        TeamUser = 1 << 10,
+        /// <summary>
+        /// The user is the Discord System user.
+        /// </summary>
+        System = 1 << 12,
+        /// <summary>
+        /// The user has the second level bug hunter badge.
+        /// </summary>
+        BugHunterLevel2 = 1 << 14,
+        /// <summary>
+        /// The user is a verified bot.
+        /// </summary>
+        VerifiedBot = 1 << 16,
+        /// <summary>
+        /// The user is a verified bot developer.
+        /// </summary>
+        VerifiedBotDeveloper = 1 << 17,
+    }
+}