Move convert package to services (#22264)

Addition to #22256

The `convert` package relies heavily on different models which is
[disallowed by our definition of
modules](https://github.com/go-gitea/gitea/blob/main/CONTRIBUTING.md#design-guideline).
This helps to prevent possible import cycles.

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

services/convert/release.go

@@ -0,0 +1,30 @@
+// Copyright 2020 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package convert
+
+import (
+	repo_model "code.gitea.io/gitea/models/repo"
+	api "code.gitea.io/gitea/modules/structs"
+)
+
+// ToRelease convert a repo_model.Release to api.Release
+func ToRelease(r *repo_model.Release) *api.Release {
+	return &api.Release{
+		ID:           r.ID,
+		TagName:      r.TagName,
+		Target:       r.Target,
+		Title:        r.Title,
+		Note:         r.Note,
+		URL:          r.APIURL(),
+		HTMLURL:      r.HTMLURL(),
+		TarURL:       r.TarURL(),
+		ZipURL:       r.ZipURL(),
+		IsDraft:      r.IsDraft,
+		IsPrerelease: r.IsPrerelease,
+		CreatedAt:    r.CreatedUnix.AsTime(),
+		PublishedAt:  r.CreatedUnix.AsTime(),
+		Publisher:    ToUser(r.Publisher, nil),
+		Attachments:  ToAttachments(r.Attachments),
+	}
+}