[DS-903] Use a new instructor field in logs instead a not used one

Steps to test you can find in related issue DS-903

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Maintaining our upgrade path is essential. Check one or the other:
- [ ] This PR provides updates via hook_update_N or other means.
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Front end fixes should be tested against all of the Open Y Themes.
- [ ] Tested against Carnation
- [ ] Tested against Lily
- [ ] Tested against Rose
- [ ] This change does not contain front-end fixes.
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