Added Register endpoints, tests and changed validation around user/sessions to match the test expectations when necessary

[azunaVT]

🎉 Add Register Endpoint (User + Session Creation)

This PR implements the /api/v1/auth/register endpoint allowing a new user to register and be authenticated immediately.

What’s included

✅ New register action in Api::V1::AuthController

• Accepts a nested user object with email, password, and password_confirmation
• Creates a User and a Session if validations pass
• Returns JSON with:
  • token for the session
  • basic user info

✅ Strong parameter handling + graceful error responses

• Returns 422 Unprocessable Entity with error messages when input is invalid
• No session is created when user creation fails

✅ Model validations for password length

• Enforces a minimum password length before allowing registration

Error cases covered

• Duplicate email
• Invalid email format
• Password confirmation mismatch
• Short password
• Missing parameters

Tests

Comprehensive integration tests have been added in:

• test/integration/api_v1_auth_register_test.rb

Validations are covered for both the success path and all expected failure scenarios.

Routes

Register is scoped under POST /api/v1/auth/register

• GET or other methods will return 404 Not Found (Rails default).
• This endpoint is a key piece of the auth MVP, enabling new users to be onboarded and obtain session tokens.