Add Visible modes function from Organisation to Users too (#16069)

You can limit or hide organisations. This pull make it also posible for users

- new strings to translte
- add checkbox to user profile form
- add checkbox to admin user.edit form
- filter explore page user search
- filter api admin and public user searches
- allow admins view "hidden" users
- add app option DEFAULT_USER_VISIBILITY
- rewrite many files to use Visibility field
- check for teams intersection
- fix context output
- right fake 404 if not visible

Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: Andrew Thornton <art27@cantab.net>

modules/convert/user_test.go

@@ -8,6 +8,7 @@ import (
 	"testing"
 
 	"code.gitea.io/gitea/models"
+	api "code.gitea.io/gitea/modules/structs"
 
 	"github.com/stretchr/testify/assert"
 )
@@ -27,4 +28,11 @@ func TestUser_ToUser(t *testing.T) {
 
 	apiUser = toUser(user1, false, false)
 	assert.False(t, apiUser.IsAdmin)
+	assert.EqualValues(t, api.VisibleTypePublic.String(), apiUser.Visibility)
+
+	user31 := models.AssertExistsAndLoadBean(t, &models.User{ID: 31, IsAdmin: false, Visibility: api.VisibleTypePrivate}).(*models.User)
+
+	apiUser = toUser(user31, true, true)
+	assert.False(t, apiUser.IsAdmin)
+	assert.EqualValues(t, api.VisibleTypePrivate.String(), apiUser.Visibility)
 }