fix: Adds server access with protected accounts (#915)

Adds a configuration file to specify protected accounts:
_Distribution/Configuration/server-access.json_
```json
{
  "newPasswordOnReset": false,
  "protectedAccounts": ["admin"]
}
```

Protected accounts are unbanned and reset to `AccessLevel.Owner` upon login.

The option `newPasswordOnReset` will create a new password for a protected account if it needs to be reset. The password is a random GUID and logged to the console.

_**Note:**_ If your player character was accidentally modified, simply make a new character to fix the old one.

Projects/UOContent/Misc/ServerAccess.cs

@@ -0,0 +1,99 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Text.Json.Serialization;
+using Server.Accounting;
+using Server.Json;
+using Server.Logging;
+
+namespace Server.Misc;
+
+public static class ServerAccess
+{
+    private static readonly ILogger logger = LogFactory.GetLogger(typeof(ServerAccess));
+    private const string _serverAccessConfigurationPath = "Configuration/server-access.json";
+    public static ServerAccessConfiguration ServerAccessConfiguration { get; private set; }
+
+    public static void SaveConfiguration()
+    {
+        var path = Path.Join(Core.BaseDirectory, _serverAccessConfigurationPath);
+        JsonConfig.Serialize(path, ServerAccessConfiguration);
+    }
+
+    public static void AddProtectedAccount(Account acct, bool save = false)
+    {
+        ServerAccessConfiguration.ProtectedAccounts.Add(acct.Username.ToLower());
+
+        if (save)
+        {
+            SaveConfiguration();
+        }
+    }
+
+    public static void RemoveProtectedAccount(Account acct, bool save = false)
+    {
+        ServerAccessConfiguration.ProtectedAccounts.Remove(acct.Username.ToLower());
+
+        if (save)
+        {
+            SaveConfiguration();
+        }
+    }
+
+    public static void Configure()
+    {
+        var path = Path.Join(Core.BaseDirectory, _serverAccessConfigurationPath);
+
+        if (!File.Exists(path))
+        {
+            return;
+        }
+
+        ServerAccessConfiguration = JsonConfig.Deserialize<ServerAccessConfiguration>(path);
+        var protectedAccounts = string.Join(", ", ServerAccessConfiguration.ProtectedAccounts);
+        logger.Information("Protected accounts registered: {0}", protectedAccounts);
+    }
+
+    public static void Initialize()
+    {
+        EventSink.AccountLogin += EventSink_ResetProtectedAccount;
+    }
+
+    public static void EventSink_ResetProtectedAccount(AccountLoginEventArgs e)
+    {
+        var username = e.Username.ToLower();
+        if (!ServerAccessConfiguration.ProtectedAccounts.Contains(username))
+        {
+            return;
+        }
+
+        var account = Accounts.GetAccount(username);
+        if (account is not { Banned: true, AccessLevel: >= AccessLevel.Owner })
+        {
+            return;
+        }
+
+        account.Banned = false;
+        account.AccessLevel = AccessLevel.Owner;
+
+        logger.Warning("Protected account \"{0}\" has been reset.", username);
+
+        if (ServerAccessConfiguration.NewPasswordOnReset)
+        {
+            var password = Guid.NewGuid().ToString();
+            logger.Warning("Protected account \"{0}\" password reset to \"{1}\"", username, password);
+            account.SetPassword(password);
+        }
+
+        e.Accepted = true;
+    }
+}
+
+public record ServerAccessConfiguration
+{
+    [JsonPropertyName("newPasswordOnReset")]
+    public bool NewPasswordOnReset { get; init; }
+
+    [JsonPropertyName("protectedAccounts")]
+    public HashSet<string> ProtectedAccounts { get; init; }
+}