Mono repo -> Master (#22553)

Combines the following repositories into one:

https://github.com/mattermost/mattermost-server
https://github.com/mattermost/mattermost-webapp
https://github.com/mattermost/focalboard
https://github.com/mattermost/mattermost-plugin-playbooks

server/channels/app/users/users_test.go

@@ -0,0 +1,89 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package users
+
+import (
+	"testing"
+
+	"github.com/mattermost/mattermost-server/v6/model"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestIsUsernameTaken(t *testing.T) {
+	th := Setup(t).InitBasic()
+	defer th.TearDown()
+
+	user := th.BasicUser
+	taken := th.service.IsUsernameTaken(user.Username)
+
+	if !taken {
+		t.Logf("the username '%v' should be taken", user.Username)
+		t.FailNow()
+	}
+
+	newUsername := "randomUsername"
+	taken = th.service.IsUsernameTaken(newUsername)
+
+	if taken {
+		t.Logf("the username '%v' should not be taken", newUsername)
+		t.FailNow()
+	}
+}
+
+func TestFirstUserPromoted(t *testing.T) {
+	th := Setup(t)
+	defer th.TearDown()
+
+	user, err := th.service.CreateUser(&model.User{
+		Username: model.NewId(),
+		Password: model.NewId(),
+		Email:    "user@example.com",
+	}, UserCreateOptions{})
+	require.NoError(t, err)
+	require.NotNil(t, user)
+
+	require.Equal(t, model.SystemAdminRoleId+" "+model.SystemUserRoleId, user.Roles)
+
+	user2, err := th.service.CreateUser(&model.User{
+		Username: model.NewId(),
+		Password: model.NewId(),
+		Email:    "user2@example.com",
+	}, UserCreateOptions{})
+	require.NoError(t, err)
+	require.NotNil(t, user2)
+
+	require.Equal(t, model.SystemUserRoleId, user2.Roles)
+
+	th.dbStore.User().PermanentDelete(user.Id)
+
+	b := &model.Bot{
+		UserId:   user2.Id,
+		OwnerId:  model.NewId(),
+		Username: model.NewId(),
+	}
+
+	_, err = th.dbStore.Bot().Save(b)
+	require.NoError(t, err)
+
+	user3, err := th.service.CreateUser(&model.User{
+		Username: model.NewId(),
+		Password: model.NewId(),
+		Email:    "user3@example.com",
+	}, UserCreateOptions{})
+	require.NoError(t, err)
+	require.NotNil(t, user3)
+
+	require.Equal(t, model.SystemAdminRoleId+" "+model.SystemUserRoleId, user3.Roles)
+
+	user4, err := th.service.CreateUser(&model.User{
+		Username: model.NewId(),
+		Password: model.NewId(),
+		Email:    "user4@example.com",
+	}, UserCreateOptions{})
+	require.NoError(t, err)
+	require.NotNil(t, user4)
+
+	require.Equal(t, model.SystemUserRoleId, user4.Roles)
+}