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/user_test.go

@@ -0,0 +1,39 @@
+// Copyright 2020 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package convert
+
+import (
+	"testing"
+
+	"code.gitea.io/gitea/models/unittest"
+	user_model "code.gitea.io/gitea/models/user"
+	api "code.gitea.io/gitea/modules/structs"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestUser_ToUser(t *testing.T) {
+	assert.NoError(t, unittest.PrepareTestDatabase())
+
+	user1 := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 1, IsAdmin: true})
+
+	apiUser := toUser(user1, true, true)
+	assert.True(t, apiUser.IsAdmin)
+	assert.Contains(t, apiUser.AvatarURL, "://")
+
+	user2 := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 2, IsAdmin: false})
+
+	apiUser = toUser(user2, true, true)
+	assert.False(t, apiUser.IsAdmin)
+
+	apiUser = toUser(user1, false, false)
+	assert.False(t, apiUser.IsAdmin)
+	assert.EqualValues(t, api.VisibleTypePublic.String(), apiUser.Visibility)
+
+	user31 := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 31, IsAdmin: false, Visibility: api.VisibleTypePrivate})
+
+	apiUser = toUser(user31, true, true)
+	assert.False(t, apiUser.IsAdmin)
+	assert.EqualValues(t, api.VisibleTypePrivate.String(), apiUser.Visibility)
+}