docs: TSDoc + reference of fulfillment service (#5761)

www/apps/docs/content/references/services/classes/Refund.mdx

@@ -8,14 +8,14 @@ import ParameterTypes from "@site/src/components/ParameterTypes"
 
 A refund represents an amount of money transfered back to the customer for a given reason. Refunds may occur in relation to Returns, Swaps and Claims, but can also be initiated by an admin for an order.
 
-## Constructors
-
-#### constructor
+## constructor
 
 `**new Refund**()`
 
 A refund represents an amount of money transfered back to the customer for a given reason. Refunds may occur in relation to Returns, Swaps and Claims, but can also be initiated by an admin for an order.
 
+___
+
 ## Properties
 
 <ParameterTypes parameters={[
@@ -129,13 +129,15 @@ A refund represents an amount of money transfered back to the customer for a giv
   }
 ]} />
 
+___
+
 ## Methods
 
-#### beforeInsert
+### beforeInsert
 
 `Private **beforeInsert**(): void`
 
-##### Returns
+#### Returns
 
 `void`