Breaking: #96149 - EXT:form EmailFinisher always uses FluidEmail 

See forge#96149

Description 

In recent versions, the EmailFinisher of EXT:form allowed sending emails with either StandaloneView or via FluidEmail, which has been introduced in TYPO3 v10. The StandaloneView option has therefore now been removed together with the Html.html and Plaintext.html templates.

Impact 

Since the EXT:form EmailFinisher is now always using FluidEmail for sending emails, the templatePathAndFilename is not evaluated anymore. For forms, which still define custom templates with this option, a fallback kicks in, sending the emails with the default EXT:form FluidEmail templates.

Also the useFluidEmail configuration option, previously used to allow a smooth migration path is now obsolete and can safely be removed from any form finisher configuration.

Affected Installations 

Installations, which have not yet switched to FluidEmail, while using custom email templates, configured with templatePathAndFilename.

Migration 

In case you use custom email templates, replace templatePathAndFilename with the templateName and templateRootPaths options. Also make sure, you have separate template files for the used formats, e.g. ContactForm.html and ContactForm.txt.