[INTS25] user admin role models

[carolynzhang18]

Notion ticket link

Create User, Admin, and Role Models + Migration Files

Implementation description

• Create new models admin and position
• Added position field to user
• Created migration file to update DB with above changes

Steps to test

1. With Docker running, run: docker exec recruitment_tools_backend node migrate up.
2. Check that you don't get any errors (I spent a solid hour whack-a-moling errors, hopefully it works without errors now).
3. In pgAdmin (or your Postgres viewer of choice), check that admins and positions are seeded with the provided data in the migration file, and check that users now has a position column (I left this nullable for backward compatibility - existing records don't have the field).

What should reviewers focus on?

Checklist

• My PR name is descriptive and in imperative tense
• My commit messages are descriptive and in imperative tense. My commits are atomic and trivial commits are squashed or fixup'd into non-trivial commits
• I have run the appropriate linter(s)
• I have requested a review from the PL, as well as other devs who have background knowledge on this PR or who will be building on top of this PR

[mxc-maggiechen]

Works great! thanks so much for doing so much work on this 👍 I think the workflow error might be a Github problem, but maybe look into it a bit? If we can't resolve it we can merge it in by bypassing permissions

[mxc-maggiechen]

if you have time, maybe create a enum for all position titles to prevent misspelling

[jeessh]

lgtm

[eric-mxrtin]