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/package.go

@@ -0,0 +1,52 @@
+// Copyright 2021 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package convert
+
+import (
+	"context"
+
+	"code.gitea.io/gitea/models/packages"
+	access_model "code.gitea.io/gitea/models/perm/access"
+	user_model "code.gitea.io/gitea/models/user"
+	api "code.gitea.io/gitea/modules/structs"
+)
+
+// ToPackage convert a packages.PackageDescriptor to api.Package
+func ToPackage(ctx context.Context, pd *packages.PackageDescriptor, doer *user_model.User) (*api.Package, error) {
+	var repo *api.Repository
+	if pd.Repository != nil {
+		permission, err := access_model.GetUserRepoPermission(ctx, pd.Repository, doer)
+		if err != nil {
+			return nil, err
+		}
+
+		if permission.HasAccess() {
+			repo = ToRepo(ctx, pd.Repository, permission.AccessMode)
+		}
+	}
+
+	return &api.Package{
+		ID:         pd.Version.ID,
+		Owner:      ToUser(pd.Owner, doer),
+		Repository: repo,
+		Creator:    ToUser(pd.Creator, doer),
+		Type:       string(pd.Package.Type),
+		Name:       pd.Package.Name,
+		Version:    pd.Version.Version,
+		CreatedAt:  pd.Version.CreatedUnix.AsTime(),
+	}, nil
+}
+
+// ToPackageFile converts packages.PackageFileDescriptor to api.PackageFile
+func ToPackageFile(pfd *packages.PackageFileDescriptor) *api.PackageFile {
+	return &api.PackageFile{
+		ID:         pfd.File.ID,
+		Size:       pfd.Blob.Size,
+		Name:       pfd.File.Name,
+		HashMD5:    pfd.Blob.HashMD5,
+		HashSHA1:   pfd.Blob.HashSHA1,
+		HashSHA256: pfd.Blob.HashSHA256,
+		HashSHA512: pfd.Blob.HashSHA512,
+	}
+}