feat(saas): implement marketplace and tenant onboarding

Tiku.Application/Tenancy/TenantOnboardingModels.cs

@@ -0,0 +1,19 @@
+namespace Tiku.Application.Tenancy;
+
+public sealed record TenantOnboardingStep(
+    string Code,
+    bool Required,
+    bool Completed,
+    string? Detail);
+
+public sealed record TenantOnboardingStatus(
+    Guid TenantId,
+    bool ReadyForStudentTraffic,
+    int CompletedRequiredSteps,
+    int RequiredSteps,
+    IReadOnlyCollection<TenantOnboardingStep> Steps);
+
+public interface ITenantOnboardingService
+{
+    Task<TenantOnboardingStatus> GetStatusAsync(Guid tenantId, CancellationToken cancellationToken = default);
+}