Add Casdoor to Server Applications

[hsluoyz]

Adds Casdoor to Server Applications, in alphabetical order between Caddy and consul.

Casdoor is a self-hosted identity and access management (IAM) / single sign-on (SSO) server written in Go, with a built-in web UI. It speaks OAuth 2.0, OIDC, SAML, CAS and LDAP, and is deployed as a server application rather than consumed as a library — the same shape as the neighbouring entries (Caddy, consul, etcd, Gitea).

Forge link: https://github.com/casdoor/casdoor
pkg.go.dev: https://pkg.go.dev/github.com/casdoor/casdoor
goreportcard.com: https://goreportcard.com/report/github.com/casdoor/casdoor
Coverage: https://app.codecov.io/gh/casdoor/casdoor

• Apache-2.0 licensed, first released 2020, actively maintained (14k+ stars)
• go.mod present, SemVer releases published regularly
• English README and documentation: https://casdoor.org/docs/overview

Checklist:

• One PR adds only one item
• Correct category and alphabetical order
• Link text is the exact project name
• Description is concise, non-promotional, and ends with a period
• Open source license, go.mod, SemVer releases, >5 months of history
• English documentation

[github-actions]

Automated Quality Checks

Required checks

✅ Repo: accessible, has go.mod and SemVer release
✅ pkg.go.dev: OK
✅ Go Report Card: OK (grade unknown)

Additional checks

✅ License: Apache-2.0
✅ Maturity: repo has 5+ months of history
✅ CI/CD: GitHub Actions workflows detected
✅ README: present
✅ Coverage: link accessible

These checks are automated and do not replace maintainer review. See CONTRIBUTING.md for full guidelines.

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PR Diff Validation

Content checks

✅ Files changed: only README.md
✅ Single item: one package added
✅ Link consistency: README link matches forge link in PR body
✅ Link text: matches repository name
✅ Description: ends with punctuation
✅ Description tone: no promotional language detected
✅ Category size: Server Applications has 38 items

Automated diff validation — does not replace maintainer review.