Test plan:
- submit a mutation with long text (long assignment description/etc)
- view the mutation log entry for that item
- it should be truncated after 256 chars
closes GQL-80
flag = GraphQL Mutation Log
Change-Id: Ibc33cc79e058b594849365ff10014899cee91afa
Reviewed-on: https://gerrit.instructure.com/204494
Tested-by: Jenkins
Reviewed-by: Rob Orton <rob@instructure.com>
QA-Review: Rob Orton <rob@instructure.com>
Product-Review: Rob Orton <rob@instructure.com>