A new backend module allows for adding and modifying a configuration for sites (= entrypoints to a website).

A site configuration has a unique (human-readable) identifier and the following additional values:

• Rootpage ID
• The base path ("Base URL" / HTTP entry point, like https://www.mydomain.com/)
• The definition of language=0 (default language) of this pagetree
• Available Languages for this pagetree and their base path (https://www.mydomain.com/fr/)
• Language Configuration (fallback, strict etc)

A site configuration is stored in typo3conf/sites/site-identifier/config.yaml.

Done:

• Create a backend module
• Create edit/create functionality based on FormEngine
• Create a "Site" object containing all values of a site
• Create a PSR-15 middleware to find the correct site
• Create Links to the frontend from backend
• Tree-based view of sites in BE module
• FormEngine: Required fields
• FormEngine: Validate identifier

ToDo:

• Use site + language logic in frontend links
• Implement fallback for &L= parameter
• Build Error Handler functionality into ErrorController
• Add caching layer
• Handle fallback logic of fallbackTypes in Languages
• Create API to persist files into folder (also ensure that the folder always exists)
• Cleanup BE module (labels etc)
• FormEngine: Cleanup "SiteConfigurationTCA" logic (do we need a ctrl section?)

Resolves: #? Releases: master