increase max_length of Mailbox.uri

in some cases like Office365 the 255 limit could be exceeded.

django_mailbox/migrations/0010_alter_mailbox_uri.py

@@ -0,0 +1,18 @@
+# Generated by Django 3.2.25 on 2026-06-23 09:18
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('django_mailbox', '0009_alter_message_eml'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='mailbox',
+            name='uri',
+            field=models.CharField(blank=True, default=None, help_text="Example: imap+ssl://myusername:mypassword@someserver <br /><br />Internet transports include 'imap' and 'pop3'; common local file transports include 'maildir', 'mbox', and less commonly 'babyl', 'mh', and 'mmdf'. <br /><br />Be sure to urlencode your username and password should they contain illegal characters (like @, :, etc).", max_length=2048, null=True, verbose_name='URI'),
+        ),
+    ]