Set the help_text id attribute to the field aria-describedby

Otherwise, the rendered HTML does contains an `aria-describedby` that
references a nonexistent element.

src/django_bootstrap5/renderers.py

@@ -403,6 +403,7 @@ def get_help_html(self):
                 context={
                     "field": self.field,
                     "help_text": help_text,
+                    "id_help_text": f"{self.field.auto_id}_helptext",
                     "layout": self.layout,
                     "show_help": self.show_help,
                 },

src/django_bootstrap5/templates/django_bootstrap5/field_help_text.html

@@ -1 +1 @@
-{% if help_text %}<div class="form-text">{{ help_text|safe }}</div>{% endif %}
+{% if help_text %}<div id="{{ id_help_text }}" class="form-text">{{ help_text|safe }}</div>{% endif %}

tests/test_bootstrap_field.py

@@ -1,6 +1,6 @@
 from django import forms
 
-from .base import BootstrapTestCase
+from .base import DJANGO_VERSION, BootstrapTestCase
 
 
 class XssTestForm(forms.Form):
@@ -24,10 +24,22 @@ def test_illegal_field(self):
     def test_show_help(self):
         html = self.render("{% bootstrap_field form.subject %}", {"form": SubjectTestForm()})
         self.assertIn("my_help_text", html)
+        if DJANGO_VERSION >= "5":
+            self.assertIn('aria-describedby="id_subject_helptext"', html)
+        self.assertIn('<div id="id_subject_helptext" class="form-text">my_help_text</div>', html)
         self.assertNotIn("<i>my_help_text</i>", html)
         html = self.render("{% bootstrap_field form.subject show_help=False %}", {"form": SubjectTestForm()})
         self.assertNotIn("my_help_text", html)
 
+    if DJANGO_VERSION >= "5":
+
+        def test_helptext_id_matches_django(self):
+            form = SubjectTestForm({})
+            django_attrs = form["subject"].build_widget_attrs({})
+            aria_describedby = django_attrs["aria-describedby"]
+            html = self.render("{% bootstrap_field form.subject %}", {"form": form})
+            self.assertIn(f'<div id="{aria_describedby}" class="form-text">my_help_text</div>', html)
+
     def test_placeholder(self):
         html = self.render("{% bootstrap_field form.subject %}", {"form": SubjectTestForm()})
         self.assertIn('type="text"', html)

tests/test_bootstrap_form.py

@@ -45,7 +45,7 @@ def test_exclude(self):
                 '<label class="form-label" for="id_required_text">Required text</label>'
                 '<input type="text" name="required_text" class="form-control"'
                 ' placeholder="Required text" required id="id_required_text">'
-                '<div class="form-text"><i>required_text_help</i>'
+                '<div id="id_required_text_helptext" class="form-text"><i>required_text_help</i>'
                 "</div>"
             ),
         )