On first boot database seeding creates MANAGED admin despite the USER table being already populated

[mulder999]

Current Behavior

Following limitation #6312, we renamed managed admin user as disabled__admin with v4 to avoid possible conflict with any OIDC user.

Steps to Reproduce

1. Convert a v4 DB whose MANAGED admin user was renamed and contains no other users
2. Start DT v5

-> Seed MANAGED admin user is created again

Expected Behavior

No seeding of admin user if other users already exists.

Dependency-Track Version

5.x

Browser

N/A

Checklist

• I have read and understand the contributing guidelines
• I have checked the existing issues for whether this defect was already reported