Reports non-string literals that are used as bundle property key.

This is hard to maintain. It is better to pass around already resolved natural language strings.

Example:


  val key =
    if (???) "property.key.1"
    else "property.key.2"

  Bundle.message(key)

Use instead:


  val string =
    if (???) Bundle.message("property.key.1")
    else Bundle.message("property.key.2")

  string