In OutputTemplate.php, a check has been added to ensure the existence of the
'QUI\\HtmlToPdf\\Document' class before using it. If the class does not exist, an error message is
logged, and an exception is thrown indicating that the html2pdf module is missing. This fix is
aimed at avoiding potential errors that may occur due to the absence of the required module.

Changed the variable name `$OutputProvider` to `$outputProvider` to adhere to camelCase naming
standards. Also moved the instantiation of `$outputProvider` inside an if block to prevent
unnecessary instantiation when `$outputProvider` is empty.

Related: pcsg/kunden/libellio/b2c/core#196

Related: pcsg/buero#491

fix: declaration of ArticleList::toHTMLWithCSS must be compatible with ArticleListUnique::toHTMLWithCSS

feat(ArticleListUnique): toHTML() can be passed to template engine and thus settings / variables can be passed on

Related: order-simple-checkout#12

Related: #105

Related: #105

Related: #105

Related: #104

fix: correctly check if translation of unit exists

See merge request !151

(cherry picked from commit 21a31f8f)

Co-authored-by: Patrick Müller <p.mueller@pcsg.de>

Related: pcsg/buero#476

Related: pcsg/buero#425

Related: pcsg/buero#456

Related: pcsg/buero#344
Related: pcsg/buero#436

Related: pcsg/buero#344
Related: pcsg/buero#436

Customer id was not passed on correctly.
So it happened that the customer id did NOT get into the erp entities.

Related: pcsg/buero#453