it is very tedious to write sling i18n resource manually in this very verbose format
instead, the goal it to write it in an very easy an compact format e.g.
java properties i18n file
json file (allows nesting for building key hierarchies)
xml file (allows nesting for building key hierarchies)
all those input files are transformed during maven build to the sling destintation format in either JCR content JSON or XML format.
a first draft of the implementation is here:
currently only JSON as output format is supported.
documentation will be added to wcm.io soon.