bug symfony#24434 [Form] Use for=ID on radio/checkbox label. (Nyholm)

This PR was merged into the 2.7 branch.

Discussion
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[Form] Use for=ID on radio/checkbox label.

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        |

I recently let Europe's leading accessibility experts (Funkanu.se) review a site of mine, they gave me (among other) this feedback.

> Putting the checkbox/radio input inside the label is great, but the label still needs the "for=ID". Screen readers like Jaws does not work properly without this attribute.

Commits
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53d7857 Use for=ID on radio/checkbox label.

Author: fabpot

src/Symfony/Bridge/Twig/Resources/views/Form/bootstrap_3_layout.html.twig

@@ -148,10 +148,14 @@
 {% endblock %}
 
 {% block checkbox_label -%}
+    {%- set label_attr = label_attr|merge({'for': id}) -%}
+
     {{- block('checkbox_radio_label') -}}
 {%- endblock checkbox_label %}
 
 {% block radio_label -%}
+    {%- set label_attr = label_attr|merge({'for': id}) -%}
+
     {{- block('checkbox_radio_label') -}}
 {%- endblock radio_label %}