<?xml version="1.0" encoding="UTF-8"?>
<domain-models xmlns="http://apps.axelor.com/xml/ns/domain-models"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://apps.axelor.com/xml/ns/domain-models http://apps.axelor.com/xml/ns/domain-models/domain-models_2.0.xsd">

  <module name="sale" package="com.axelor.apps.sale.db"/>

  <entity name="SaleConfig" lang="java" cachable="true">
  	<integer name="importId"/>
    <string name="name" title="Name" required="true"/>
    <string name="code" title="Code" unique="true"/>
    
    <many-to-one name="company" ref="com.axelor.apps.base.db.Company" title="Company" unique="true"/>

  	<integer name="saleOrderInvoicingTypeSelect" title="Sales order invoicing type" selection="sale.order.invoicing.type.select"/>
  	
  </entity>
  
</domain-models>

<?xml version="1.0" encoding="UTF-8"?>
<domain-models xmlns="http://apps.axelor.com/xml/ns/domain-models"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://apps.axelor.com/xml/ns/domain-models http://apps.axelor.com/xml/ns/domain-models/domain-models_2.0.xsd">

  <module name="sale" package="com.axelor.apps.sale.db"/>

  <entity name="SaleConfig" lang="java" cachable="true">
  	<integer name="importId"/>
    
    <many-to-one name="company" ref="com.axelor.apps.base.db.Company" title="Company" required="true" unique="true"/>

  	<integer name="saleOrderInvoicingTypeSelect" title="Sales order invoicing type" selection="sale.order.invoicing.type.select"/>
  	
  </entity>
  
</domain-models>

Add required contrains on sale domains
Add required contrains on sale domains
