feat: allow a honey batch to be split across multiple storage containers

A batch that doesn't fit in one container (e.g. 125 kg across 5 x 25 kg
buckets) had no way to be represented - HoneyBatch.storageContainerId
is a single nullable FK. Adds HoneyBatchContainerAllocation as an
additive join table (container + amount per batch), independent of the
existing single-container/relocate() flow which still covers the
simple one-container case unchanged.

- GET/PUT/DELETE /honey-batches/:id/containers[/:containerId], reusing
  the existing honey-batches:relocate permission.
- Assigning a container is an upsert (@@unique on batch+container), and
  the total assigned is validated against the batch's own amount when
  known.
- New "Aufteilung auf mehrere Behälter" card on the honey batch detail
  page, alongside (not replacing) the existing storage card.

Co-Authored-By: Claude Sonnet 5 <[email protected]>

ApiCore-Backend/src/honey-batches/honey-batches.service.spec.ts

@@ -1,4 +1,4 @@
-import { NotFoundException } from '@nestjs/common';
+import { BadRequestException, NotFoundException } from '@nestjs/common';
 import { HoneyBatchesService } from './honey-batches.service';
 import { PrismaService } from '../prisma/prisma.service';
 import { AuditLogService } from '../audit/audit-log.service';
@@ -17,6 +17,12 @@ describe('HoneyBatchesService', () => {
     honeyMeasurement: { create: jest.Mock };
     storageContainer: { findUnique: jest.Mock };
     honeyBatchRelocation: { create: jest.Mock; findMany: jest.Mock };
+    honeyBatchContainerAllocation: {
+      findMany: jest.Mock;
+      findUnique: jest.Mock;
+      upsert: jest.Mock;
+      delete: jest.Mock;
+    };
     $transaction: jest.Mock;
   };
   let auditLog: { record: jest.Mock };
@@ -57,6 +63,12 @@ describe('HoneyBatchesService', () => {
       honeyMeasurement: { create: jest.fn() },
       storageContainer: { findUnique: jest.fn() },
       honeyBatchRelocation: { create: jest.fn(), findMany: jest.fn() },
+      honeyBatchContainerAllocation: {
+        findMany: jest.fn().mockResolvedValue([]),
+        findUnique: jest.fn(),
+        upsert: jest.fn(),
+        delete: jest.fn(),
+      },
       $transaction: jest.fn(),
     };
     auditLog = { record: jest.fn() };
@@ -199,4 +211,147 @@ describe('HoneyBatchesService', () => {
       expect(findArg.where.honeyBatchId).toBe('batch-1');
     });
   });
+
+  describe('setContainerAllocation', () => {
+    it('throws NotFoundException when the container does not exist', async () => {
+      prisma.honeyBatch.findUnique.mockResolvedValue(honeyBatch);
+      prisma.storageContainer.findUnique.mockResolvedValue(null);
+
+      await expect(
+        service.setContainerAllocation(
+          'batch-1',
+          'missing',
+          { amount: 25 },
+          'user-1',
+        ),
+      ).rejects.toBeInstanceOf(NotFoundException);
+    });
+
+    it('allows splitting the batch amount across multiple containers (125 kg / 5 x 25 kg)', async () => {
+      prisma.honeyBatch.findUnique.mockResolvedValue({
+        ...honeyBatch,
+        amount: 125,
+      });
+      prisma.storageContainer.findUnique.mockResolvedValue({
+        id: 'bucket-5',
+      });
+      prisma.honeyBatchContainerAllocation.findMany.mockResolvedValue([
+        { storageContainerId: 'bucket-1', amount: 25 },
+        { storageContainerId: 'bucket-2', amount: 25 },
+        { storageContainerId: 'bucket-3', amount: 25 },
+        { storageContainerId: 'bucket-4', amount: 25 },
+      ]);
+      prisma.honeyBatchContainerAllocation.upsert.mockResolvedValue({
+        id: 'allocation-5',
+        honeyBatchId: 'batch-1',
+        storageContainerId: 'bucket-5',
+        amount: 25,
+      });
+
+      await service.setContainerAllocation(
+        'batch-1',
+        'bucket-5',
+        { amount: 25 },
+        'user-1',
+      );
+
+      expect(prisma.honeyBatchContainerAllocation.upsert).toHaveBeenCalledWith({
+        where: {
+          honeyBatchId_storageContainerId: {
+            honeyBatchId: 'batch-1',
+            storageContainerId: 'bucket-5',
+          },
+        },
+        create: {
+          honeyBatchId: 'batch-1',
+          storageContainerId: 'bucket-5',
+          amount: 25,
+        },
+        update: { amount: 25 },
+        include: { storageContainer: true },
+      });
+    });
+
+    it('rejects an allocation that would exceed the batch amount', async () => {
+      prisma.honeyBatch.findUnique.mockResolvedValue({
+        ...honeyBatch,
+        amount: 100,
+      });
+      prisma.storageContainer.findUnique.mockResolvedValue({ id: 'bucket-1' });
+      prisma.honeyBatchContainerAllocation.findMany.mockResolvedValue([
+        { storageContainerId: 'bucket-2', amount: 80 },
+      ]);
+
+      await expect(
+        service.setContainerAllocation(
+          'batch-1',
+          'bucket-1',
+          { amount: 30 },
+          'user-1',
+        ),
+      ).rejects.toBeInstanceOf(BadRequestException);
+      expect(
+        prisma.honeyBatchContainerAllocation.upsert,
+      ).not.toHaveBeenCalled();
+    });
+
+    it('re-assigning the same container overwrites its own amount rather than double-counting it', async () => {
+      prisma.honeyBatch.findUnique.mockResolvedValue({
+        ...honeyBatch,
+        amount: 100,
+      });
+      prisma.storageContainer.findUnique.mockResolvedValue({ id: 'bucket-1' });
+      // findMany excludes the container being set (storageContainerId: { not: ... }),
+      // so its own prior amount never counts against itself here.
+      prisma.honeyBatchContainerAllocation.findMany.mockResolvedValue([]);
+      prisma.honeyBatchContainerAllocation.upsert.mockResolvedValue({
+        id: 'allocation-1',
+        honeyBatchId: 'batch-1',
+        storageContainerId: 'bucket-1',
+        amount: 90,
+      });
+
+      await expect(
+        service.setContainerAllocation(
+          'batch-1',
+          'bucket-1',
+          { amount: 90 },
+          'user-1',
+        ),
+      ).resolves.toBeDefined();
+    });
+  });
+
+  describe('removeContainerAllocation', () => {
+    it('throws NotFoundException when no allocation exists for that container', async () => {
+      prisma.honeyBatch.findUnique.mockResolvedValue(honeyBatch);
+      prisma.honeyBatchContainerAllocation.findUnique.mockResolvedValue(null);
+
+      await expect(
+        service.removeContainerAllocation('batch-1', 'bucket-1', 'user-1'),
+      ).rejects.toBeInstanceOf(NotFoundException);
+    });
+
+    it('deletes the allocation and records an audit entry', async () => {
+      prisma.honeyBatch.findUnique.mockResolvedValue(honeyBatch);
+      prisma.honeyBatchContainerAllocation.findUnique.mockResolvedValue({
+        id: 'allocation-1',
+        honeyBatchId: 'batch-1',
+        storageContainerId: 'bucket-1',
+        amount: 25,
+      });
+
+      await service.removeContainerAllocation('batch-1', 'bucket-1', 'user-1');
+
+      expect(prisma.honeyBatchContainerAllocation.delete).toHaveBeenCalledWith({
+        where: { id: 'allocation-1' },
+      });
+      expect(auditLog.record).toHaveBeenCalledWith(
+        expect.objectContaining({
+          entityType: 'HoneyBatchContainerAllocation',
+          action: 'DELETE',
+        }),
+      );
+    });
+  });
 });