Block MSPs from adding SM to a managed org

src/Core/Services/Implementations/OrganizationService.cs

@@ -410,6 +410,11 @@ public class OrganizationService : IOrganizationService
         var secretsManagerPlan = StaticStore.SecretManagerPlans.FirstOrDefault(p => p.Type == signup.Plan);
         if (signup.UseSecretsManager)
         {
+            if (provider)
+            {
+                throw new BadRequestException(
+                    "Organizations with a Managed Service Provider do not support Secrets Manager.");
+            }
             ValidateSecretsManagerPlan(secretsManagerPlan, signup);
         }