Add Note to Todo GraphQL Type

What does this MR do and why?

This adds the note to the GraphQL Type for Todos

It is only present if the todo was generated by a note (directly_addressed or mentioned), in the other cases, the note field will have the value null

Rest API MR: !89299 (closed)

Screenshots or screen recordings

How to set up and validate locally

1. Checkout the branch
2. Start GDK
3. Log in to GDK GitLab
4. make sure you have at least one todo with type directly_adressed or mentioned
5. visit http://127.0.0.1:3000/-/graphql-explorer (or whatever host you have in your setup)

6. query {
     currentUser {
       todos {
         nodes {
           action
           note {
             body
             # Include any other fields you are interested in verifying
             __typename
           }
         }
       }
     }
   }

MR acceptance checklist

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