Add init link.

API/ROLAC.API/Services/IInvitationService.cs

@@ -0,0 +1,28 @@
+using ROLAC.API.DTOs.Invitations;
+using ROLAC.API.Entities;
+
+namespace ROLAC.API.Services;
+
+public interface IInvitationService
+{
+    /// <summary>
+    /// Generates a single-use, 7-day invitation link for a member. Auto-creates the member's
+    /// login account (no password) when none exists, and revokes any prior unused invitation for
+    /// that account. Returns the raw token (shown once) and its expiry.
+    /// Throws <see cref="InvalidOperationException"/> when the member is missing or has no email.
+    /// </summary>
+    Task<CreateInvitationResult> CreateAsync(CreateInvitationRequest request);
+
+    /// <summary>Checks whether a raw token is still usable, without mutating it.</summary>
+    Task<ValidateInvitationResult> ValidateAsync(string rawToken);
+
+    /// <summary>
+    /// Consumes an invitation: validates the token, sets the account password (enforcing the
+    /// Identity policy), and marks the invitation used. Returns the account on success, or an
+    /// error message describing why it failed (invalid/expired/used token or a policy violation).
+    /// </summary>
+    Task<(AppUser? User, string? Error)> AcceptAsync(string rawToken, string newPassword);
+
+    /// <summary>E-mails an already-generated invitation link to the member via IEmailService.</summary>
+    Task SendEmailAsync(int memberId, string link);
+}