[docs] Add/update DB schemas as per new additions in backend-pb

[jarp0l]

Some tables have been added added, some have been updated, but docs/diagrams/db_schema.d2 doesn't reflect the changes. Check migrations in backend/pb/migrations for the latest schemas: https://github.com/jarp0l/browser-ext-mon/tree/33-featbe-add-db-schemas-as-per-6/backend/pb/migrations

Schemas to add:

• internal_services

Schemas to update:

• users
• organizations

[jarp0l]

Still making changes to docs/diagrams/db_schema.d2 remaining.