Free price: Allow to suggest a different price than the minimum (#3666)

* Free price: Allow to suggest a different price than the minimum

* Full implementation

* Widget tests

* Add min values to titles

src/pretix/base/migrations/0248_item_free_price_suggestion.py

@@ -0,0 +1,22 @@
+# Generated by Django 4.2.4 on 2023-10-25 12:01
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("pretixbase", "0247_checkinlist"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="item",
+            name="free_price_suggestion",
+            field=models.DecimalField(decimal_places=2, max_digits=13, null=True),
+        ),
+        migrations.AddField(
+            model_name="itemvariation",
+            name="free_price_suggestion",
+            field=models.DecimalField(decimal_places=2, max_digits=13, null=True),
+        ),
+    ]