Add GetLogoutUrl method for SSO logout

[Copilot]

The SDK was missing the logout URL method referenced in the Casdoor SSO documentation.

Changes

• url.go: Added GetLogoutUrl(redirectUri string) client method
• url_global.go: Added global wrapper function
• url_test.go: Added test coverage for both variants

API

// Client method
client := casdoorsdk.NewClient(endpoint, clientId, clientSecret, cert, org, app)
logoutUrl := client.GetLogoutUrl("http://example.com/home")
// Returns: http://localhost:8000/api/logout?redirect_uri=http%3A%2F%2Fexample.com%2Fhome

// Global function
casdoorsdk.InitConfig(endpoint, clientId, clientSecret, cert, org, app)
logoutUrl := casdoorsdk.GetLogoutUrl("http://example.com/home")

// Without redirect
logoutUrl := casdoorsdk.GetLogoutUrl("")
// Returns: http://localhost:8000/api/logout

Follows existing URL method patterns (GetSigninUrl, GetSignupUrl). Redirect URI is URL-encoded when provided.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• demo.casdoor.com
  • Triggering command: /tmp/go-build3080996299/b001/casdoorsdk.test /tmp/go-build3080996299/b001/casdoorsdk.test -test.testlogfile=/tmp/go-build3080996299/b001/testlog.txt -test.paniconexit0 -test.timeout=10m0s (dns block)
• www.casdoor.org
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node /home/REDACTED/work/_temp/ghcca-node/node/bin/node --enable-source-maps /home/REDACTED/work/_temp/copilot-developer-action-main/dist/index.js (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

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This section details on the original issue you should resolve

<issue_title>SSO Logout Using Casdoor SDK</issue_title>
<issue_description>I found the following description in the documentation:
https://www.casdoor.org/docs/session/single-sign-out#using-casdoor-sdks

It states that I can use the Go SDK to perform logout, but in practice I couldn’t find such a method in the SDK.

Did I miss something, or is there an error in the documentation?</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes SSO Logout Using Casdoor SDK #222

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[hsluoyz]

@lzgzhyf is this what you want?

[lzgzhyf]

I am currently manually calling the /sso-logout endpoint in the code to log out, and it works fine. What is the difference compared to /logout?