FEAT #8346 Unit tests + refactoring

modules/attachments/attachments_content.php

modules/attachments/view_attachment.php

rest/index.php

src/app/attachment/controllers/AttachmentController.php

src/app/contact/controllers/ContactController.php

src/app/convert/controllers/ConvertPdfController.php

...app/signatureBook/controllers/SignatureBookController.php

src/core/lang/lang-en.php

src/core/lang/lang-fr.php

src/frontend/app/signature-book.component.ts

src/frontend/css/maarch-material.css

test/unitTests/app/resource/ResControllerTest.php