fix: race condition when setting bot token and ignoring banned users

There is still another race condition but this should severly limit the
surface area of the issue. We need to centralize where the bot token is
refreshed instead of allowing 2 separate threads to compete for it.

We always wanted to ignore banned users but I forget to exclude them
from the mod list.

Author: ProgrammingByPermutation

src/Nullinside.Api.TwitchBot/Services/MainService.cs

@@ -152,6 +152,13 @@ protected override Task ExecuteAsync(CancellationToken stoppingToken) {
             if (null == usersWithBotEnabled) {
               continue;
             }
+            
+            // Get the list of users that are banned.
+            List<User>? bannedUsers = await GetBannedUsers(db, stoppingToken);
+            if (null == bannedUsers) {
+              bannedUsers = Enumerable.Empty<User>().ToList();
+            }
+            var bannedUserIds = bannedUsers.Select(u => u.TwitchId).ToList();
 
             // Get the bot user's information.
             User? botUser = await db.Users.AsNoTracking()
@@ -173,6 +180,8 @@ protected override Task ExecuteAsync(CancellationToken stoppingToken) {
 
               // Trim channels we aren't a mod in
               IEnumerable<TwitchModeratedChannel> moddedChannels = await botApi.GetUserModChannels(Constants.BotId);
+              moddedChannels = moddedChannels.Where(m => !bannedUserIds.Contains(m.broadcaster_id)).ToList();
+              
               usersWithBotEnabled = usersWithBotEnabled
                 .Where(u => moddedChannels
                   .Select(m => m.broadcaster_id)
@@ -281,6 +290,23 @@ orderby user.TwitchLastScanned
       .AsNoTracking()
       .ToListAsync(stoppingToken);
   }
+  
+  /// <summary>
+  ///   Retrieve all users that are banned from using the bot.
+  /// </summary>
+  /// <param name="db">The database.</param>
+  /// <param name="stoppingToken">The stopping token.</param>
+  /// <returns>The list of users with the bot enabled.</returns>
+  private async Task<List<User>?> GetBannedUsers(INullinsideContext db, CancellationToken stoppingToken) {
+    return await
+      (from user in db.Users
+        orderby user.TwitchLastScanned
+        where user.TwitchId != Constants.BotId &&
+              user.IsBanned
+        select user)
+      .AsNoTracking()
+      .ToListAsync(stoppingToken);
+  }
 
   /// <summary>
   ///   Performs the scan on a user.
@@ -299,16 +325,16 @@ private async Task DoScan(User user, User botUser, CancellationToken stoppingTok
     using (IServiceScope scope = _serviceScopeFactory.CreateAsyncScope()) {
       await using (var db = scope.ServiceProvider.GetRequiredService<INullinsideContext>()) {
         // Get the API
-        ITwitchApiProxy? botApi = await db.ConfigureApiAndRefreshToken(botUser, this._api, stoppingToken);
-        if (null == _botRules || null == user.TwitchConfig || null == botApi) {
+        this._api.Configure(botUser);
+        if (null == _botRules || null == user.TwitchConfig) {
           return;
         }
 
         // Run the rules that scan the chats and the accounts.
         foreach (IBotRule rule in _botRules) {
           try {
             if (rule.ShouldRun(user.TwitchConfig)) {
-              await rule.Handle(user, user.TwitchConfig, botApi, db, stoppingToken);
+              await rule.Handle(user, user.TwitchConfig, this._api, db, stoppingToken);
             }
           }
           catch (Exception e) {