feat: add BACKEND_URL configuration for OAuth redirect

[MODSetter]

Description

feat: add BACKEND_URL configuration for OAuth redirect

Motivation and Context

To override google oauth redirect.

Screenshots

API Changes

• This PR includes API changes

Change Type

• Bug fix
• New feature
• Performance improvement
• Refactoring
• Documentation
• Dependency/Build system
• Breaking change
• Other (specify):

Testing Performed

• Tested locally
• Manual/QA verification

Checklist

• Follows project coding standards and conventions
• Documentation updated as needed
• Dependencies updated as needed
• No lint/build errors or new warnings
• All relevant tests are passing

High-level PR Summary

This PR adds a new optional BACKEND_URL environment variable to allow overriding the OAuth redirect URL for Google authentication. When BACKEND_URL is configured, the Google OAuth router uses a custom redirect URL pointing to {BACKEND_URL}/auth/google/callback instead of the default, which is useful for scenarios where the backend needs to force HTTPS redirects or handle proxy/load balancer configurations.

⏱️ Estimated Review Time: 5-15 minutes

💡 Review Order Suggestion

Order	File Path
1	surfsense_backend/app/config/__init__.py
2	surfsense_backend/app/app.py

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Project	Deployment	Preview	Comments	Updated (UTC)
surf-sense-frontend	Ready	Preview	Comment	Oct 31, 2025 6:54am

[coderabbitai]

Caution

Review failed

The pull request is closed.

Walkthrough

The pull request introduces environment-based configuration for Google OAuth redirect URL handling. A new BACKEND_URL configuration option is added and used to conditionally modify the OAuth router construction, enabling the redirect URI to be dynamically set when the environment variable is present.

Changes

Cohort / File(s)	Summary
Configuration surfsense_backend/app/config/__init__.py	Added BACKEND_URL configuration attribute sourced from environment variable
OAuth Router Setup surfsense_backend/app/app.py	Google OAuth router construction now branches conditionally: includes redirect_url parameter when BACKEND_URL is set; uses original construction otherwise

Sequence Diagram(s)

sequenceDiagram
    participant Env as Environment
    participant Config as Config Class
    participant App as app.py
    participant Router as OAuth Router
    
    Env->>Config: BACKEND_URL (if present)
    Config->>App: config.BACKEND_URL
    alt BACKEND_URL is set
        App->>Router: Create with redirect_url={BACKEND_URL}/auth/google/callback
    else BACKEND_URL not set
        App->>Router: Create with default is_verified_by_default=True
    end

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Estimated Code Review Effort

🎯 2 (Simple) | ⏱️ ~10 minutes

• The BACKEND_URL addition follows existing configuration patterns
• Conditional router construction is straightforward and localized to one location
• No complex logic or multi-file dependencies introduced

Poem

🐰 A backend URL hops into place,
OAuth redirects find their grace,
Configuration branches left and right,
Environment variables set it tight,
Bounce—authentication takes flight!

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch dev

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📜 Recent review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 5174f21 and 4a3f681.

📒 Files selected for processing (2)

• surfsense_backend/app/app.py (1 hunks)
• surfsense_backend/app/config/__init__.py (1 hunks)

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[recurseml]

Review by RecurseML

🔍 Review performed on 5174f21..4a3f681

✨ No bugs found, your code is sparkling clean

✅ Files analyzed, no issues (2)

• surfsense_backend/app/app.py
• surfsense_backend/app/config/__init__.py