fix(ST-511): add createWithCodeRetry helper to handle P2002 race on auto codes

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

lib/code-server.ts

@@ -1,5 +1,43 @@
+import { Prisma } from '@prisma/client'
 import { prisma } from '@/lib/prisma'
 
+const MAX_AUTO_CODE_ATTEMPTS = 3
+
+function isCodeUniqueConflict(error: unknown): boolean {
+  if (!(error instanceof Prisma.PrismaClientKnownRequestError)) return false
+  if (error.code !== 'P2002') return false
+  const target = (error.meta as { target?: string[] | string } | undefined)?.target
+  if (!target) return false
+  if (Array.isArray(target)) return target.includes('code')
+  return target.includes('code')
+}
+
+/**
+ * Generate an auto code, then run the create. If the insert collides with an
+ * existing code (P2002 on the code column), regenerate and retry up to a small
+ * number of attempts. Protects against the SELECT-MAX → INSERT race when two
+ * concurrent requests pick the same next number.
+ */
+export async function createWithCodeRetry<T>(
+  generate: () => Promise<string>,
+  create: (code: string) => Promise<T>,
+): Promise<T> {
+  let lastError: unknown
+  for (let attempt = 0; attempt < MAX_AUTO_CODE_ATTEMPTS; attempt++) {
+    const code = await generate()
+    try {
+      return await create(code)
+    } catch (e) {
+      if (isCodeUniqueConflict(e)) {
+        lastError = e
+        continue
+      }
+      throw e
+    }
+  }
+  throw lastError ?? new Error('Kon geen unieke code genereren')
+}
+
 const STORY_AUTO_RE = /^ST-(\d+)$/
 const PBI_AUTO_RE = /^PBI-(\d+)$/