add Upload URL to release API (#26663)

- Resolves https://codeberg.org/forgejo/forgejo/issues/580
- Return a `upload_field` to any release API response, which points to
the API URL for uploading new assets.
- Adds unit test.
- Adds integration testing to verify URL is returned correctly and that
upload endpoint actually works

---------

Co-authored-by: Gusted <postmaster@gusted.xyz>

services/convert/release.go

@@ -22,6 +22,7 @@ func ToAPIRelease(ctx context.Context, repo *repo_model.Repository, r *repo_mode
 		HTMLURL:      r.HTMLURL(),
 		TarURL:       r.TarURL(),
 		ZipURL:       r.ZipURL(),
+		UploadURL:    r.APIUploadURL(),
 		IsDraft:      r.IsDraft,
 		IsPrerelease: r.IsPrerelease,
 		CreatedAt:    r.CreatedUnix.AsTime(),

services/convert/release_test.go

@@ -0,0 +1,28 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package convert
+
+import (
+	"testing"
+
+	"code.gitea.io/gitea/models/db"
+	repo_model "code.gitea.io/gitea/models/repo"
+	"code.gitea.io/gitea/models/unittest"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestRelease_ToRelease(t *testing.T) {
+	assert.NoError(t, unittest.PrepareTestDatabase())
+
+	repo1 := unittest.AssertExistsAndLoadBean(t, &repo_model.Repository{ID: 1})
+	release1 := unittest.AssertExistsAndLoadBean(t, &repo_model.Release{ID: 1})
+	release1.LoadAttributes(db.DefaultContext)
+
+	apiRelease := ToAPIRelease(db.DefaultContext, repo1, release1)
+	assert.NotNil(t, apiRelease)
+	assert.EqualValues(t, 1, apiRelease.ID)
+	assert.EqualValues(t, "https://try.gitea.io/api/v1/repos/user2/repo1/releases/1", apiRelease.URL)
+	assert.EqualValues(t, "https://try.gitea.io/api/v1/repos/user2/repo1/releases/1/assets", apiRelease.UploadURL)
+}