feat: Vikunja to-do app (#128)

Vikunja is fast self-hostable to-do app.

Reviewed-on: https://git.selfprivacy.org/SelfPrivacy/selfprivacy-nixos-config/pulls/128
Reviewed-by: Inex Code <inex.code@selfprivacy.org>
Co-authored-by: nhnn <nhnn@nhnn.dev>
Co-committed-by: nhnn <nhnn@nhnn.dev>

sp-modules/vikunja/load-client-secret-from-env.patch

@@ -0,0 +1,33 @@
+diff --git a/pkg/modules/auth/openid/providers.go b/pkg/modules/auth/openid/providers.go
+index 5e14c1b31..769dc96e8 100644
+--- a/pkg/modules/auth/openid/providers.go
++++ b/pkg/modules/auth/openid/providers.go
+@@ -17,6 +17,7 @@
+ package openid
+ 
+ import (
++	"os"
+ 	"regexp"
+ 	"strconv"
+ 	"strings"
+@@ -129,12 +130,19 @@ func getProviderFromMap(pi map[string]interface{}) (provider *Provider, err erro
+ 	if scope == "" {
+ 		scope = "openid profile email"
+ 	}
++
++	clientsecret, err := os.ReadFile(os.Getenv("SP_VIKUNJA_CLIENT_SECRET_PATH"))
++
++	if err != nil {
++		panic(err)
++	}
++
+ 	provider = &Provider{
+ 		Name:            pi["name"].(string),
+ 		Key:             k,
+ 		AuthURL:         pi["authurl"].(string),
+ 		OriginalAuthURL: pi["authurl"].(string),
+-		ClientSecret:    pi["clientsecret"].(string),
++		ClientSecret:    strings.TrimSuffix(string(clientsecret), "\n"),
+ 		LogoutURL:       logoutURL,
+ 		Scope:           scope,
+ 	}