fix(changelog): Don't check the user changelog twice

[nickvergessen]

☑️ Resolves

• Related
  

Explanation

There was a simple race condition previously with 2 requests R1 and R2:

• R1: handle()
• R1: userHasNewChangelog() compares X0 with count()
• R2: handle()
• R2: userHasNewChangelog() compares X0 with count()
• R1: updateChangelog()
• R1: getChangelogForUser() reads X0
• R1: setUserValue() sets X1 with precondition X0
• R2: updateChangelog()
• R2: getChangelogForUser() reads X1 💥
• R2: setUserValue() sets X1 with precondition X1

🏁 Checklist

• ⛑️ Tests (unit and/or integration) are included or not possible
• 📘 API documentation in docs/ has been updated or is not required
• 🔖 Capability is added or not needed

[nickvergessen]

/backport to stable30

[Antreesy]

LGTM