feat: Make PostLoginRedirectUri to support absolute uri (#122)

* feat(post-login-redirect): support for PostLoginRedirectUri to use absolute uri

* refactor(post-login-redirect): improve readability and cleanliness

* refactor(post-login-redirect): adapt EnsureAbsoluteUrl in utils to handle prefix

Author: jvitor83

main.go

@@ -394,9 +394,7 @@ func (toa *TraefikOidcAuth) redirectToProvider(rw http.ResponseWriter, req *http
 	if redirectUrlFromQuery := req.URL.Query().Get("redirect_uri"); toa.Config.LoginUri != "" && strings.HasPrefix(req.RequestURI, toa.Config.LoginUri) && redirectUrlFromQuery != "" {
 		redirectUrl = redirectUrlFromQuery
 	} else if toa.Config.PostLoginRedirectUri != "" {
-		host := utils.GetFullHost(req)
-		postLoginUri, _ := strings.CutPrefix(toa.Config.PostLoginRedirectUri, "/")
-		redirectUrl = fmt.Sprintf("%s/%s", host, postLoginUri)
+		redirectUrl = utils.EnsureAbsoluteUrl(req, toa.Config.PostLoginRedirectUri)
 	} else {
 		host := utils.GetFullHost(req)
 		redirectUrl = fmt.Sprintf("%s%s", host, req.RequestURI)

utils/utils.go

@@ -72,6 +72,11 @@ func EnsureAbsoluteUrl(req *http.Request, url string) string {
 		return url
 	} else {
 		host := GetFullHost(req)
+
+		if !strings.HasPrefix(url, "/") {
+			url = "/" + url
+		}
+
 		return host + url
 	}
 }