fixes

Author: mluukkai

src/content/8/en/part8c.md

@@ -203,7 +203,7 @@ Mutation: {
 }
 ```
 
-We have also added the Mongoose error and the data that caused the error to the <i>extensions</i> object that is used to convey more info about the cause of the error to the caller.
+We have also added the Mongoose error and the data that caused the error to the <i>extensions</i> object that is used to convey more info about the cause of the error to the caller. The frontend can then display this information to the user, who can try the operation again with a better input. 
 
 The code of the backend can be found on [Github](https://github.com/fullstack-hy2020/graphql-phonebook-backend/tree/part8-4), branch <i>part8-4</i>.
 

src/content/8/fi/osa8c.md

@@ -204,7 +204,7 @@ Mutation: {
 }
 ```
 
-Mongoosen virheen tiedot ja ongelman aiheuttanut data on nyt liitetty poikkeuksen konfiguraatio-olioon <i>extensions</i>, näin ne saadaan välitettyä kutsujalle.
+Mongoosen virheen tiedot ja ongelman aiheuttanut data on nyt liitetty poikkeuksen konfiguraatio-olioon <i>extensions</i>, näin ne saadaan välitettyä kutsujalle. 
 
 Backendin koodi on kokonaisuudessaan [GitHubissa](https://github.com/fullstack-hy2020/graphql-phonebook-backend/tree/part8-4), branchissa <i>part8-4</i>.