Implement Certificate Generation & Verification System

Community & Support: [LinkedIn Group](https://www.linkedin.com/groups/14656108/) · [Slack #project-nest](https://owasp.slack.com/archives/project-nest)

Active project leaders: Arkadii Yakovets -- [GitHub](https://github.com/arkid15r/) · [LinkedIn](https://www.linkedin.com/in/arkid15r/) · [Slack](https://owasp.slack.com/team/U060W3NKLTF); Kate Golovanova -- [GitHub](https://github.com/kasya/) · [LinkedIn](https://www.linkedin.com/in/kate-golovanova/) · [Slack](https://owasp.slack.com/team/U07PWB1JZ6Z)

[Contributing](https://github.com/owasp/nest/blob/main/CONTRIBUTING.md) · [Code of Conduct](https://github.com/owasp/nest/blob/main/CODE_OF_CONDUCT.md) · [GSoC Mentors](https://github.com/owasp/nest/blob/main/MENTORS.md)

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### Description

Implement certificate generation for contributors when they reach a new recognition tier.

Certificates should be automatically generated on tier upgrades and support verification and download.

### Certificate Generation

Generate PDF certificates when a contributor reaches a new tier.

Certificates should include:

- contributor name
- Nest user ID
- tier
- score at issuance
- contribution summary
- unique certificate ID
- issue date
- OWASP branding

### Certificate Verification

Implement a public certificate verification endpoint.

The system should:

- verify certificate validity
- check revocation status
- return certificate details

### Certificate Download

Implement a secure download endpoint for certificates.

Downloads should only be accessible to:

- certificate owner
- staff/admin users

**Are you going to work on implementing this?**

- [x] Yes
- [ ] No