refactor(router): appstate as trait in authentication

[racnan]

Type of Change

• [ ] Bugfix
• [ ] New feature
• [ ] Enhancement
• [X] Refactoring
• [ ] Dependency updates

Description

• Making AppState generic in authenticate_and_fetch.
• Making functions public.

Additional Changes

• [ ] This PR modifies the database schema
• [ ] This PR modifies application configuration/environment variables

Motivation and Context

• Making authentication_and_fetch usable for extending projects.

How did you test it?

Checklist

• [X] I formatted the code cargo +nightly fmt --all
• [X] I addressed lints thrown by cargo clippy
• [X] I reviewed submitted code
• [ ] I added unit tests for my changes where possible
• [ ] I added a CHANGELOG entry if applicable