Introduce ITenantDatabaseSchemaMigrator.

framework/src/Volo.Abp.MultiTenancy/Volo/Abp/MultiTenancy/NullTenantDatabaseSchemaMigrator.cs

@@ -0,0 +1,13 @@
+using System.Threading.Tasks;
+using Volo.Abp.DependencyInjection;
+
+namespace Volo.Abp.MultiTenancy
+{
+    public class NullTenantDatabaseSchemaMigrator : ITenantDatabaseSchemaMigrator, ISingletonDependency
+    {
+        public Task MigrateAsync()
+        {
+            return Task.CompletedTask;
+        }
+    }
+}

framework/src/Volo.Abp.MultiTenancy/Volo/Abp/MultiTenancy/TenantDatabaseSchemaMigrator.cs

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+using System.Threading.Tasks;
+
+namespace Volo.Abp.MultiTenancy
+{
+    public interface ITenantDatabaseSchemaMigrator
+    {
+        /// <summary>
+        /// Set Current Tenant before calling this method.
+        /// </summary>
+        /// <returns></returns>
+        Task MigrateAsync();
+    }
+}