Problem/Motivation
It's possible to define a custom content type by placing necessary files into a custom module's directory structure under config/[install | optional]. One might also want that content type to be translatable and may have even gone through the work to define some of the translations. If those translations are placed in config/[install | optional]/language/[language-code], then they should be pulled into the system when the module is enabled. Currently it's not the case, because for `install` folder system ignores scalar values and processes only array values and for the `optional` folder system installs config only in default collection, ignoring all other available collections.
Proposed resolution
Process translation files correctly, when module is installed separately or along with profile installation, by processing all values in configs and taking all available collections for optional configs.
Remaining tasks
Review the patch, give feedback and fix the patch,
API changes
Within current patch function installOptionalConfig() receives 3rd parameter with collection name.