docs: update validation doc

Author: slax57

Diff for: admin/validation.md

@@ -5,7 +5,7 @@ API Platform Admin manages automatically two types of validation: client-side va
 ## Client-side Validation
 
 If the API documentation indicates that a field is mandatory,
-API Platform Admin will automatically add a [required client-side validation](https://marmelab.com/react-admin/CreateEdit.html#per-input-validation-built-in-field-validators).
+API Platform Admin will automatically add a [required client-side validation](https://marmelab.com/react-admin/Validation.html#per-input-validation-built-in-field-validators).
 
 For instance, with API Platform as backend, if you write the following:
 
@@ -25,7 +25,7 @@ class Book
 }
 ```
 
-If you create a new book and touch the "Title" field without typing, you will see:
+If you create a new book and try to submit without filling the "Title" field, you will see:
 
 ![Required title field](images/required-field.png)
 
@@ -34,8 +34,7 @@ If you create a new book and touch the "Title" field without typing, you will se
 When the form is submitted and if submission errors are received,
 API Platform Admin will automatically show the errors for the corresponding fields.
 
-To do so, it uses the [submission validation](https://marmelab.com/react-admin/CreateEdit.html#submission-validation) feature of React Admin,
-and the mapping between the response and the fields is done by the [schema analyzer](components.md#schemaanalyzer) with its method `getSubmissionErrors`.
+To do so, it uses the [Server-Side Validation](https://marmelab.com/react-admin/Validation.html#server-side-validation) feature of React Admin, and the mapping between the response and the fields is done by the [schema analyzer](components.md#hydra-schema-analyzer) with its method `getSubmissionErrors`.
 
 API Platform is supported by default, but if you use another backend, you will need to override the `getSubmissionErrors` method.