Update migrate-to-composite-field.md

docs/cookbook/migrate-to-composite-field.md

@@ -2,7 +2,7 @@
 
 Sometimes you start with table containing values, which you then see have dependency on each other. As happened with [Stamp object](https://gitlab.grifart.cz/ivy/server/-/merge_requests/222/diffs#note_69354) (originally named `auditTrail`).
 
-## 1. migrating database
+### 1. migrating database
 
 ```sql
 -- prepare new data type in PostgreSQL
@@ -27,6 +27,8 @@ ALTER TABLE "clinic"."patient"
 	DROP COLUMN "createdBy";
 ```
 
+### 2. Mapper
+
 And add mapping of new field. It is useful to use PostgreSQL tools for composite & array types. This helper class will provide you logic for (de)serializing these composite types into standard SQL query.
 
 ```php
@@ -49,4 +51,4 @@ And add mapping of new field. It is useful to use PostgreSQL tools for composite
 				);
 			},
 		);
-```
\ No newline at end of file
+```