Merge branch 'develop' into 'feat/17671/develop'

.gitlab-ci.yml

lang/en.json

lang/fr.json

phpunit.xml

rest/index.php

sql/data_fr.sql

sql/structure.sql

src/app/email/controllers/EmailController.php

src/app/group/controllers/GroupController.php

src/app/group/controllers/PrivilegeController.php

src/app/group/models/GroupPrivilegeModel.php

src/app/history/controllers/HistoryController.php

src/app/user/controllers/SignatureController.php

src/app/user/controllers/UserController.php

src/app/user/models/UserGroupModel.php

src/app/user/models/UserModel.php

src/core/controllers/AuthenticationController.php

src/core/models/DatabasePDO.php

src/core/models/PasswordModel.php

src/frontend/app/administration/group/group.component.html