Update RadioSelectButtonGroup() with form validation and non-horizont…

…al alignment.

docs/widgets.rst

@@ -8,8 +8,6 @@ A form widget is available for displaying radio buttons as a Bootstrap 5 button
 RadioSelectButtonGroup
 ~~~~~~~~~~~~~~~~~~~~~~
 
-*Known issue: This widget currently renders as a regular Bootstrap 5 RadioSelect.*
-
 This renders a form ChoiceField as a Bootstrap 5 button group in the `primary` Bootstrap 5 color.
 
 .. code:: django

src/django_bootstrap5/templates/django_bootstrap5/widgets/radio_select_button_group.html

@@ -1,16 +1,20 @@
-<div{% if widget.attrs.id %} id="{{ widget.attrs.id }}"{% endif %} class="btn-group" role="group">
-  {% for group, options, index in widget.optgroups %}
-    {% for option in options %}
-      <input type="{{ option.type }}"
-             class="{{ widget.attrs.class|add:' btn-check' }}"
-             autocomplete="off"
-             name="{{ option.name }}"
-             id="{{ option.attrs.id }}"
-             {% if option.value != None %} value="{{ option.value|stringformat:'s' }}"
-              {% if option.attrs.checked %} checked="checked"{% endif %}{% endif %}
-             {% if widget.attrs.disabled %} disabled{% endif %}
-             {% if widget.required %} required{% endif %}>
-      <label class="btn btn-outline-primary" for="{{ option.attrs.id }}">{{ option.label }}</label>
-    {% endfor %}
-  {% endfor %}
+{% load django_bootstrap5 %}
+{% bootstrap_server_side_validation_class widget as server_side_validation_class %}
+<div{% include "django/forms/widgets/attrs.html" %}>
+    <div class="btn-group" role="group">
+        {% for group, options, index in widget.optgroups %}
+            {% for option in options %}
+                <input type="{{ option.type }}"
+                       class="{{ widget.attrs.class|add:' btn-check' }}"
+                       autocomplete="off"
+                       name="{{ option.name }}"
+                       id="{{ option.attrs.id }}"
+                        {% if option.value != None %} value="{{ option.value|stringformat:'s' }}"
+                            {% if option.attrs.checked %} checked="checked"{% endif %}{% endif %}
+                        {% if widget.attrs.disabled %} disabled{% endif %}
+                        {% if widget.required %} required{% endif %}>
+                <label class="btn btn-outline-primary" for="{{ option.attrs.id }}">{{ option.label }}</label>
+            {% endfor %}
+        {% endfor %}
+    </div>
 </div>