88 create a new erd diagram

Definition of Done

For every submission to the codebase, check that it meets the DoD below.

[x] Code fulfils the user story and scenarios set out in the github task and UI prototype.
[x] The feature has been thoroughly manually tested. (Ask other devs to give some fresh eyes on this as you go.)
[x] All tests run and passed from terminal. Any broken tests fixed, not disabled or skipped.

npm test
[x] Tests added or updated where appropriate. (Be pragmatic about adding new tests, think; how critical is this module or function? If this function broke due to changes, how would it affect the user experience?)
[x] eslint run and passes. Any issues fixed.

npm run lint
[x] PR created in Github.
[ ] Two peer reviews from other devs.
[x] One peer review from one of the teachers.
[ ] After all the peer review comments are addressed, the branch is merged to main!