feat: Implement USD limits per time period per user

[NightMachinery]

Feature Request: Per-User Monthly Spending Limits

Description:

I appreciate the global request limits added in Issue #20. However, I need the ability to set customizable monthly spending limits per user.

Use Case:

I want to give my family and friends access to LLMs through Open WebUI, but I need to control costs by limiting how much each user can spend per month in USD.

Potential Solutions and Considerations:

• Per-User Spending Limits:

  • Allow setting individual monthly spending caps for each user.

• Cost Estimation:

  • Since determining the exact cost per model usage can be challenging, consider using heuristics such as:
    • Estimating costs based on token usage or number of requests.
    • Assigning a fixed cost per action or session.

• Alternative Approaches:

  • Implement per-user limits on usage metrics like tokens or requests, which correlate with costs.

Benefits:

• Helps manage and predict overall spending.
• Enables sharing access with others without unexpected expenses.

Thank you for considering this feature request.