fix default strategy for unique keys

Author: sdebruyn

dbt/include/sqlserver/macros/materializations/models/incremental/incremental_strategies.sql

@@ -0,0 +1,9 @@
+{% macro sqlserver__get_incremental_default_sql(arg_dict) %}
+
+    {% if arg_dict["unique_key"] %}
+        {% do return(get_incremental_delete_insert_sql(arg_dict)) %}
+    {% else %}
+        {% do return(get_incremental_append_sql(arg_dict)) %}
+    {% endif %}
+
+{% endmacro %}