many fixes and improvements - rework for modules/ and common/

feat(emailer): add Postmark and Resend providers

backend/Modules/Memberships/Contracts/IMembershipNotifier.cs

@@ -0,0 +1,26 @@
+namespace Hutopy.Modules.Memberships.Contracts;
+
+public interface IMembershipNotifier
+{
+    Task NotifyCheckoutSessionCompleted(string stripeSessionId, string stripeSubscriptionId,
+        string userId,
+        string creatorId,
+        string tierId,
+        CancellationToken cancellationToken = default);
+
+    Task NotifyPaymentSucceedAsync(
+        string stripeSubscriptionId,
+        string hostedInvoiceUrl,
+        decimal amount,
+        string currency,
+        CancellationToken cancellationToken = default);
+
+    Task NotifySubscriptionUpdatedAsync(
+        string subscriptionId,
+        DateTimeOffset? endDate,
+        CancellationToken cancellationToken = default);
+
+    Task NotifySubscriptionDeletedAsync(
+        string subscriptionId,
+        CancellationToken cancellationToken = default);
+}