feat: refactor inventory and recipe services for improved error handling and code reuse; add systematic backend review plan

backend/src/receipt-alias/receipt-alias.service.ts

@@ -1,4 +1,4 @@
-import { ForbiddenException, Injectable } from '@nestjs/common';
+import { ForbiddenException, Injectable, NotFoundException } from '@nestjs/common';
 import { PrismaService } from '../prisma/prisma.service';
 import { CreateReceiptAliasDto } from './dto/create-receipt-alias.dto';
 
@@ -25,59 +25,48 @@ export class ReceiptAliasService {
 
   async upsert(dto: CreateReceiptAliasDto, userId: number, role: string) {
     const normalized = dto.receiptName.toLowerCase().trim();
-
     const wantsGlobal = dto.isGlobal === true;
+
     if (wantsGlobal && role !== 'admin') {
       throw new ForbiddenException('Endast admin kan skapa globala alias');
     }
 
-    if (wantsGlobal) {
-      const existing = await this.prisma.receiptAlias.findFirst({
-        where: { receiptName: normalized, isGlobal: true },
-      });
-
-      if (existing) {
-        return this.prisma.receiptAlias.update({
-          where: { id: existing.id },
-          data: { productId: dto.productId },
-        });
-      }
-
-      return this.prisma.receiptAlias.create({
-        data: {
-          receiptName: normalized,
-          productId: dto.productId,
-          isGlobal: true,
-          ownerId: null,
-        },
-      });
-    }
+    return this.upsertAliasRecord(
+      normalized,
+      dto.productId,
+      wantsGlobal ? null : userId,
+      wantsGlobal,
+    );
+  }
 
+  private async upsertAliasRecord(
+    receiptName: string,
+    productId: number,
+    ownerId: number | null,
+    isGlobal: boolean,
+  ) {
     const existing = await this.prisma.receiptAlias.findFirst({
-      where: { receiptName: normalized, ownerId: userId, isGlobal: false },
+      where: isGlobal
+        ? { receiptName, isGlobal: true }
+        : { receiptName, ownerId, isGlobal: false },
     });
 
     if (existing) {
       return this.prisma.receiptAlias.update({
         where: { id: existing.id },
-        data: { productId: dto.productId },
+        data: { productId },
       });
     }
 
     return this.prisma.receiptAlias.create({
-      data: {
-        receiptName: normalized,
-        productId: dto.productId,
-        ownerId: userId,
-        isGlobal: false,
-      },
+      data: { receiptName, productId, ownerId, isGlobal },
     });
   }
 
   async remove(id: number, userId: number, role: string) {
     const alias = await this.prisma.receiptAlias.findUnique({ where: { id } });
     if (!alias) {
-      return this.prisma.receiptAlias.delete({ where: { id } });
+      throw new NotFoundException(`Aliaspost med id ${id} hittades inte`);
     }
 
     const canDelete =