Merge pull request #390 from devforth/AdminForth/573

docs: add raw SQL usage example

Author: ivictbor

adminforth/documentation/docs/tutorial/03-Customization/11-dataApi.md

@@ -123,6 +123,39 @@ const users = await admin.resource('adminuser').list(
 );
 ```
 
+## Using a raw SQL in queries.
+
+Rarely you might want to add ciondition for some exotic SQL but still want to keep the rest of API.
+Technically it happened that AdminForth allows you to do this also
+
+```js
+const minUgcAge = 18;
+const usersWithNoUgcAccess = await admin.resource('adminuser').list(
+  [
+    Filters.NEQ('role', 'Admin'), 
+    {
+       insecureRawSQL: `(user_meta->>'age') < ${sqlstring.escape(minUgcAge)}`
+    }
+
+  ], 15, 0, Sorts.DESC('createdAt')
+);
+
+This will produce next SQL query:
+```
+
+```
+SELECT *
+FROM "adminuser"
+WHERE "role" != 'Admin'
+  AND (user_meta->>'age') < 18
+ORDER BY "createdAt" DESC
+LIMIT 15 OFFSET 0;
+
+```
+
+
+Finds users with age less then 18 from meta field which should be a JSONB field in Postgress.
+
 ## Create a new item in database
 
 Signature: