Add get actions runner registration token for API routes, repo, org, user and global level (#27144)

Replace #23761

---------

Co-authored-by: Denys Konovalov <kontakt@denyskon.de>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>

routers/api/v1/shared/runners.go

@@ -0,0 +1,32 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package shared
+
+import (
+	"errors"
+	"net/http"
+
+	actions_model "code.gitea.io/gitea/models/actions"
+	"code.gitea.io/gitea/modules/context"
+	"code.gitea.io/gitea/modules/util"
+)
+
+// RegistrationToken is response related to registeration token
+// swagger:response RegistrationToken
+type RegistrationToken struct {
+	Token string `json:"token"`
+}
+
+func GetRegistrationToken(ctx *context.APIContext, ownerID, repoID int64) {
+	token, err := actions_model.GetLatestRunnerToken(ctx, ownerID, repoID)
+	if errors.Is(err, util.ErrNotExist) || (token != nil && !token.IsActive) {
+		token, err = actions_model.NewRunnerToken(ctx, ownerID, repoID)
+	}
+	if err != nil {
+		ctx.InternalServerError(err)
+		return
+	}
+
+	ctx.JSON(http.StatusOK, RegistrationToken{Token: token.Token})
+}