feat(auth): LdapBindMode.User options and validation

ZB.MOM.WW.Auth/src/ZB.MOM.WW.Auth.Abstractions/Ldap/LdapContracts.cs

@@ -4,6 +4,20 @@ namespace ZB.MOM.WW.Auth.Abstractions.Ldap;
 
 public enum LdapTransport { Ldaps, StartTls, None }
 
+/// <summary>How <see cref="LdapOptions"/> authenticates a sign-in.</summary>
+public enum LdapBindMode
+{
+    /// <summary>Bind as the service account, search for the user, re-bind as the user (0.3.0 behaviour).</summary>
+    ServiceAccount,
+
+    /// <summary>
+    /// Bind as the signing-in user (identity built from <see cref="LdapOptions.UserBindTemplate"/>);
+    /// a successful bind authenticates them, and the same connection reads their own entry for groups.
+    /// No service account is used.
+    /// </summary>
+    User,
+}
+
 public sealed record LdapOptions
 {
     public bool Enabled { get; init; } = true;
@@ -19,6 +33,27 @@ public sealed record LdapOptions
     public string GroupAttribute { get; init; } = "memberOf";
     public int ConnectionTimeoutMs { get; init; } = 10_000;
 
+    /// <summary>
+    /// Selects the authentication flow. <see cref="LdapBindMode.ServiceAccount"/> (the default) is the
+    /// 0.3.0 bind-then-search-then-bind flow; <see cref="LdapBindMode.User"/> binds as the user and needs
+    /// no <see cref="ServiceAccountDn"/> / <see cref="ServiceAccountPassword"/>.
+    /// </summary>
+    public LdapBindMode BindMode { get; init; } = LdapBindMode.ServiceAccount;
+
+    /// <summary>
+    /// <see cref="LdapBindMode.User"/> only: the simple-bind identity, with <c>{0}</c> replaced by the
+    /// normalised login name — e.g. <c>{0}@example.com</c> (UPN) or <c>EXAMPLE\{0}</c>. Must contain
+    /// <c>{0}</c> exactly once.
+    /// </summary>
+    public string UserBindTemplate { get; init; } = "";
+
+    /// <summary>
+    /// <see cref="LdapBindMode.User"/> only: when <see langword="true"/> (default) a login typed as
+    /// <c>DOMAIN\name</c> or <c>name@suffix</c> is reduced to <c>name</c>; when <see langword="false"/>
+    /// such input is refused as bad credentials without contacting the directory.
+    /// </summary>
+    public bool AcceptDomainQualifiedNames { get; init; } = true;
+
     /// <summary>
     /// Ordered fallback LDAP endpoints tried when the primary (and any earlier fallback)
     /// fails with a system-side error (connect/TLS, service-account bind, or search).