fix: standardize naming oidcSub

[jekabs-karklins]

Description

This PR standardizes the naming convention of 'oidc_sub' to 'oidcSub' across the codebase.

Motivation and Context

The change is required to maintain a consistent naming convention in the codebase. This standardization will improve code readability and maintainability.

Changes

• Renamed 'oidc_sub' to 'oidcSub' in User.ts, UserQueries.ts, BasicUserDetails.ts, basicUserInformation.graphql, and useBlankVisitRegistration.ts.
• This change does not introduce any new functionality or modify existing behavior, it is purely a refactoring of variable names for consistency.

How Has This Been Tested?

Fixes Jira Issue

https://jira.ess.eu//browse/

Depends On

Tests included/Docs Updated?

• I have added tests to cover my changes.
• All relevant doc has been updated

[Copilot]

Pull request overview

Standardizes the BasicUserDetails “OIDC subject” field naming from oidc_sub to oidcSub across the backend model/GraphQL type and the frontend GraphQL fragment + a visit-registration stub.

Changes:

• Renamed BasicUserDetails.oidc_sub → BasicUserDetails.oidcSub in backend model, queries, and GraphQL resolver type.
• Updated frontend basicUserDetails fragment to request oidcSub.
• Updated visit registration stub user shape to use oidcSub.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
apps/frontend/src/hooks/visit/useBlankVisitRegistration.ts	Updates stubbed user object to use oidcSub.
apps/frontend/src/graphql/user/fragment.basicUserInformation.graphql	Renames requested field from oidc_sub to oidcSub in the fragment.
apps/backend/src/resolvers/types/BasicUserDetails.ts	Renames exposed GraphQL field to oidcSub.
apps/backend/src/queries/UserQueries.ts	Switches query-to-model mapping to read user.oidcSub.
apps/backend/src/models/User.ts	Renames BasicUserDetails constructor property to oidcSub.