Fix package access for admins and inactive users (#21580)

I noticed an admin is not allowed to upload packages for other users
because `ctx.IsSigned` was not set.
I added a check for `user.IsActive` and `user.ProhibitLogin` too because
both was not checked. Tests enforce this now.

Co-authored-by: Lauris BH <lauris@nix.lv>

tests/integration/api_packages_container_test.go

@@ -471,6 +471,10 @@ func TestPackageContainer(t *testing.T) {
 
 				assert.Equal(t, fmt.Sprintf("%d", len(blobContent)), resp.Header().Get("Content-Length"))
 				assert.Equal(t, blobDigest, resp.Header().Get("Docker-Content-Digest"))
+
+				req = NewRequest(t, "HEAD", fmt.Sprintf("%s/blobs/%s", url, blobDigest))
+				addTokenAuthHeader(req, anonymousToken)
+				MakeRequest(t, req, http.StatusOK)
 			})
 
 			t.Run("GetBlob", func(t *testing.T) {