Add option to filter board cards by labels and assignees (#31999)

Works in both organization and repository project boards

Fixes #21846

Replaces #21963
Replaces #27117
 

![image](https://github.com/user-attachments/assets/1837ace8-3de2-444f-a153-e166bd0da2c0)

**Note** that implementation was made intentionally to work same as in
issue list so that URL can be bookmarked for quick access with
predefined filters in URL

routers/web/shared/user/helper_test.go

@@ -0,0 +1,26 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package user
+
+import (
+	"testing"
+
+	"code.gitea.io/gitea/models/user"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestMakeSelfOnTop(t *testing.T) {
+	users := MakeSelfOnTop(nil, []*user.User{{ID: 2}, {ID: 1}})
+	assert.Len(t, users, 2)
+	assert.EqualValues(t, 2, users[0].ID)
+
+	users = MakeSelfOnTop(&user.User{ID: 1}, []*user.User{{ID: 2}, {ID: 1}})
+	assert.Len(t, users, 2)
+	assert.EqualValues(t, 1, users[0].ID)
+
+	users = MakeSelfOnTop(&user.User{ID: 2}, []*user.User{{ID: 2}, {ID: 1}})
+	assert.Len(t, users, 2)
+	assert.EqualValues(t, 2, users[0].ID)
+}