Tweak NEWS.md entry about additional_metadata, other_keys

Author: brookslogan

NEWS.md

@@ -6,8 +6,11 @@ Pre-1.0.0 numbering scheme: 0.x will indicate releases, while 0.x.y will indicat
 
 ## Breaking changes
 
-- `additional_metadata` is no longer used in `as_epi_df()` construction. 
-  `other_keys` is promoted to be an argument directly.
+- `additional_metadata` is no longer accepted in `as_epi_df()` or
+   `as_epi_archive()`. Use the new `other_keys` arg to specify additional key
+   columns, such as age group columns or other demographic breakdowns.
+   Miscellaneous metadata are no longer handled by `epiprocess`, but you can use
+   R's built-in `attr<-` instead for a similar feature.
 
 ## Improvements