Add flexible grant reimbursement categories

Replace the hardcoded grant reimbursement types with a configurable model. Each
conference can now define its own reimbursement categories with custom:
- Names and descriptions
- Maximum amounts per category
- Default inclusion settings
- Category types (travel, ticket, accommodation, other)

This allows for more flexible grant management where each conference can
customize their reimbursement options while maintaining data consistency
through the category system. It replaces the old hardcoded `ApprovedType`
choices with a dynamic model-based approach.

Author: estyxx

backend/grants/admin.py

@@ -30,7 +30,7 @@
 )
 from schedule.models import ScheduleItem
 from submissions.models import Submission
-from .models import Grant, GrantConfirmPendingStatusProxy
+from .models import Grant, GrantConfirmPendingStatusProxy, GrantReimbursementCategory
 from django.db.models import Exists, OuterRef, F
 from pretix import user_has_admission_ticket
 
@@ -393,6 +393,12 @@ def queryset(self, request, queryset):
         return queryset
 
 
+@admin.register(GrantReimbursementCategory)
+class GrantReimbursementCategoryAdmin(ConferencePermissionMixin, admin.ModelAdmin):
+    list_display = ("__str__", "max_amount", "category", "included_by_default")
+    list_filter = ("conference", "category", "included_by_default")
+
+
 @admin.register(Grant)
 class GrantAdmin(ExportMixin, ConferencePermissionMixin, admin.ModelAdmin):
     change_list_template = "admin/grants/grant/change_list.html"

backend/grants/migrations/0029_grantreimbursementcategory.py

@@ -0,0 +1,33 @@
+# Generated by Django 5.1.4 on 2025-06-04 15:20
+
+import django.db.models.deletion
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('conferences', '0054_conference_frontend_revalidate_secret_and_more'),
+        ('grants', '0028_remove_grant_pretix_voucher_id_and_more'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='GrantReimbursementCategory',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('name', models.CharField(max_length=100)),
+                ('description', models.TextField(blank=True, null=True)),
+                ('max_amount', models.DecimalField(decimal_places=0, help_text='Maximum amount for this category', max_digits=6)),
+                ('category', models.CharField(choices=[('travel', 'Travel'), ('ticket', 'Ticket'), ('accommodation', 'Accommodation'), ('other', 'Other')], max_length=20)),
+                ('included_by_default', models.BooleanField(default=False, help_text='Automatically include this category in grants by default')),
+                ('conference', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name='reimbursement_categories', to='conferences.conference')),
+            ],
+            options={
+                'verbose_name': 'Grant Reimbursement Category',
+                'verbose_name_plural': 'Grant Reimbursement Categories',
+                'ordering': ['conference', 'category'],
+                'unique_together': {('conference', 'category')},
+            },
+        ),
+    ]

backend/grants/models.py

@@ -14,6 +14,43 @@ def of_user(self, user):
         return self.filter(user=user)
 
 
+class GrantReimbursementCategory(models.Model):
+    """
+    Define types of reimbursements available for a grant (e.g., Travel, Ticket, Accommodation).
+    """
+
+    class Category(models.TextChoices):
+        TRAVEL = "travel", _("Travel")
+        TICKET = "ticket", _("Ticket")
+        ACCOMMODATION = "accommodation", _("Accommodation")
+        OTHER = "other", _("Other")
+
+    conference = models.ForeignKey(
+        "conferences.Conference",
+        on_delete=models.CASCADE,
+        related_name="reimbursement_categories",
+    )
+    name = models.CharField(max_length=100)
+    description = models.TextField(blank=True, null=True)
+    max_amount = models.DecimalField(
+        max_digits=6, decimal_places=0, help_text=_("Maximum amount for this category")
+    )
+    category = models.CharField(max_length=20, choices=Category.choices)
+    included_by_default = models.BooleanField(
+        default=False,
+        help_text="Automatically include this category in grants by default",
+    )
+
+    def __str__(self):
+        return f"{self.name} ({self.conference.name})"
+
+    class Meta:
+        verbose_name = _("Grant Reimbursement Category")
+        verbose_name_plural = _("Grant Reimbursement Categories")
+        unique_together = [("conference", "category")]
+        ordering = ["conference", "category"]
+
+
 class Grant(TimeStampedModel):
     # TextChoices
     class Status(models.TextChoices):

backend/grants/tests/factories.py

@@ -2,7 +2,7 @@
 from factory.django import DjangoModelFactory
 
 from conferences.tests.factories import ConferenceFactory
-from grants.models import Grant
+from grants.models import Grant, GrantReimbursementCategory
 from helpers.constants import GENDERS
 from users.tests.factories import UserFactory
 from countries import countries
@@ -11,6 +11,24 @@
 import random
 
 
+class GrantReimbursementCategoryFactory(DjangoModelFactory):
+    """
+    Factory for creating GrantReimbursementCategory instances for testing.
+    """
+
+    class Meta:
+        model = GrantReimbursementCategory
+
+    conference = factory.SubFactory(ConferenceFactory)
+    name = factory.Faker("word")
+    description = factory.Faker("sentence")
+    max_amount = factory.fuzzy.FuzzyDecimal(50, 500, precision=2)
+    category = factory.fuzzy.FuzzyChoice(
+        GrantReimbursementCategory.CategoryType.choices, getter=lambda x: x[0]
+    )
+    included_by_default = factory.Faker("boolean")
+
+
 class GrantFactory(DjangoModelFactory):
     class Meta:
         model = Grant