[FIX] base: cannot specify 24-hour clock format and meridian

- Settings > manage languages > english > Set time format to `%H:%M:%S %p`
> Save
- Install Planning app > go to list view > Try modifying a time manually
(without using the widget which pops up).

Issue:
When trying to save the new time, an error pops up: `Can't include meridiem
when specifying 24-hour format`.

While parsing the new date, the `luxon` library throws this error to
prevent wrong hour values, such as `17 AM`.

Fix:
Prevent the user from inputting both `%H` and `%p` in the same time format
and display a warning notification.

opw-3038797

closes odoo/odoo#106846

Signed-off-by: Xavier Morel (xmo) <xmo@odoo.com>

odoo/addons/base/models/res_lang.py

@@ -81,6 +81,23 @@ class Lang(models.Model):
                                             'Please refer to the list of allowed directives, '
                                             'displayed when you edit a language.'))
 
+    @api.onchange('time_format', 'date_format')
+    def _onchange_format(self):
+        warning = {
+            'warning': {
+                'title': _("Using 24-hour clock format with AM/PM can cause issues."),
+                'message': _("Changing to 12-hour clock format instead."),
+                'type': 'notification'
+            }
+        }
+        for lang in self:
+            if lang.date_format and "%H" in lang.date_format and "%p" in lang.date_format:
+                lang.date_format = lang.date_format.replace("%H", "%I")
+                return warning
+            if lang.time_format and "%H" in lang.time_format and "%p" in lang.time_format:
+                lang.time_format = lang.time_format.replace("%H", "%I")
+                return warning
+
     @api.constrains('grouping')
     def _check_grouping(self):
         warning = _('The Separator Format should be like [,n] where 0 < n :starting from Unit digit. '