Add recurring investments API support

[parthchandak02]

Summary

This PR adds comprehensive support for Robinhood's recurring investments feature, allowing users to programmatically create, retrieve, update, and cancel recurring investment schedules.

Changes

New Module: robin_stocks/robinhood/recurring_investments.py

• get_recurring_investments() - Fetch all recurring investments (supports filtering by account or asset types)
• create_recurring_investment() - Create new recurring investments with configurable frequency and amount
• update_recurring_investment() - Update existing investments (pause/resume, change amount/frequency)
• cancel_recurring_investment() - Cancel recurring investments (uses PATCH with state="deleted")
• get_next_investment_date() - Get the next investment date for a given frequency

Modified Files

• robin_stocks/robinhood/urls.py - Added URL helper functions for recurring investment endpoints
• robin_stocks/robinhood/__init__.py - Exported all new recurring investment functions

Technical Details

• Endpoint: Uses bonfire.robinhood.com/recurring_schedules/ (discovered through reverse engineering)
• Authentication: Uses existing @login_required decorator and session management
• Patterns: Follows existing library patterns and conventions
• Error Handling: Proper error handling and status code checking

Testing

✅ Tested with real Robinhood account:

• Successfully fetched 100+ existing recurring investments
• Created new recurring investments
• Updated recurring investments (pause/resume)
• Cancelled recurring investments
• Verified all functions work correctly

Example Usage

n import robin_stocks.robinhood as rh

rh.login(username='...', password='...')

Get all recurring investments

investments = rh.get_recurring_investments()

Create a new recurring investment

rh.create_recurring_investment('TSLA', 50.0, frequency='weekly')

Pause an investment

rh.update_recurring_investment(schedule_id, state='paused')

Cancel an investment

rh.cancel_recurring_investment(schedule_id)## Notes

• Uses unofficial endpoint (Robinhood doesn't provide a public API)
• Consistent with existing robin_stocks approach since Robinhood doesn't offer a public API
• All functions follow library conventions and patterns