Add admin auth middleware

[nanu-c]

Type of change

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [x] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [x] This change requires a documentation update

Description

This introduces an auth admin + vendor middleware. This needs a re-import to keycloak because of the missing openid scope that isn't standard in keycloak 20 anymore. That means the userinfo endpoint doesn't work.

Bonus: enable the linter #33

Checklist:

• [x] I have commented my code (or ChatGPT did), particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [ ] My changes generate no new warnings, neither in my IDE nor in my browser
• [ ] I have added tests that prove my fix is effective or that my feature works

[nanu-c]

Everything looks good except for a little typo. Only thing not working for me locally is testing it in my own docker container. Either I get /api/vendors/ expected status code 200, got 401: Unauthorized or Error logging in Keycloak admin could not get token: Post "http://localhost:8080/realms/master/protocol/openid-connect/token": dial tcp 127.0.0.1:8080: connect: connection refused

the keycloak url in the .env must be http://keycloak:8080