fix: add missing checks to several API and web handlers (#39501) (#39507)

Backport #39501 by @silverwind

Several handlers skipped checks that their sibling routes or settings
already enforce. This brings them in line.

- Push mirror API honors `DISABLE_NEW_PUSH` and checks the caller's
permission
- Media API serves small files with the usual content headers
- Issue attachment API ignores comment attachments
- Push-to-create respects `FORCE_PRIVATE`
- Profile feeds and follow actions respect `ENABLE_FEED` and owner
visibility
- Tag delete route refuses release tags
- Refresh token grant only accepts refresh tokens
- Gitea migrations bound the source's page size

Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: bircni <bircni@icloud.com>

routers/web/repo/release.go

@@ -660,6 +660,11 @@ func deleteReleaseOrTag(ctx *context.Context, isDelTag bool) {
 		return
 	}
 
+	if isDelTag && !rel.IsTag {
+		ctx.HTTPError(http.StatusConflict, "a tag attached to a release cannot be deleted directly")
+		return
+	}
+
 	if err := release_service.DeleteReleaseByID(ctx, ctx.Repo.Repository, rel, ctx.Doer, isDelTag); err != nil {
 		if release_service.IsErrProtectedTagName(err) {
 			ctx.Flash.Error(ctx.Tr("repo.release.tag_name_protected"))

routers/web/repo/release_test.go

@@ -4,6 +4,7 @@
 package repo
 
 import (
+	"net/http"
 	"net/http/httptest"
 	"testing"
 
@@ -21,6 +22,21 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+func TestDeleteTagRetainsReleaseAndAttachments(t *testing.T) {
+	unittest.PrepareTestEnv(t)
+	ctx, resp := contexttest.MockContext(t, "POST user2/repo1/tags/delete?id=1")
+	contexttest.LoadUser(t, ctx, 2)
+	contexttest.LoadRepo(t, ctx, 1)
+	release := unittest.AssertExistsAndLoadBean(t, &repo_model.Release{ID: 1})
+	attachment := unittest.AssertExistsAndLoadBean(t, &repo_model.Attachment{ID: 9, ReleaseID: 1})
+
+	DeleteTag(ctx)
+
+	assert.Equal(t, http.StatusConflict, resp.Code)
+	assert.Equal(t, release, unittest.AssertExistsAndLoadBean(t, &repo_model.Release{ID: 1}))
+	assert.Equal(t, attachment, unittest.AssertExistsAndLoadBean(t, &repo_model.Attachment{ID: 9}))
+}
+
 func TestNewReleasePost(t *testing.T) {
 	unittest.PrepareTestEnv(t)