feat: add endpoint to get a user's own organization

[pdevine]

Summary

This change modifies the GET /api/organizations/:id endpoint to now support GET /api/organizations/self similar to how GET /api/identities/self works. The user does not need to be an infra support admin to retrieve their own organization details.

Additionally, the created and updated fields inside of the JSON response are now being properly updated (instead of returning null values), and a unit test for the endpoint has been added.

Checklist

• Wrote appropriate unit tests
• Considered security implications of the change
• Updated associated docs where necessary
• Updated associated configuration where necessary
• Change is backwards compatible if it needs to be (user can upgrade without manual steps?)
• Nothing sensitive logged
• Considered data migrations for smooth upgrades

[ssoroka]

might be simpler to add organization id to the identity/self endpoint?

[pdevine]

I did look at adding it to GET /api/users/self initially, but it seemed like more work since we'd still have to look up the org name, and then mutate the users API for each of the fields. This endpoint already had everything we needed, other than we were missing unit tests and the self ID.