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

feat(emailer): add Postmark and Resend providers

backend/Modules/Creators/Contracts/CreatorReference.cs

@@ -0,0 +1,9 @@
+namespace Hutopy.Modules.Creators.Contracts;
+
+public record CreatorReference(
+    Guid Id,
+    string Name,
+    string? PortraitUrl,
+    bool OnboardingComplete,
+    bool AcceptCharges,
+    string? StripeAccountId);

backend/Modules/Creators/Contracts/ICreatorLookup.cs

@@ -0,0 +1,6 @@
+namespace Hutopy.Modules.Creators.Contracts;
+
+public interface ICreatorLookup
+{
+    Task<CreatorReference?> GetCreatorAsync(Guid creatorId, CancellationToken cancellationToken = default);
+}