litellm feat(grafana_dashboard): enable datasource selection via templating

This commit updates the Grafana dashboard configuration to include a datasource template variable. This allows users to dynamically select the datasource directly within the Grafana dashboard, improving flexibility and user experience.

Title

Enable datasource selection via templating

Relevant issues

N/A (This introduces a new feature)

Pre-Submission checklist

Please complete all items before asking a LiteLLM maintainer to review your PR

[ ] I have Added testing in the tests/litellm/ directory, Adding at least 1 test is a hard requirement - see details
[x] I have added a screenshot of my new test passing locally
[x] My PR passes all unit tests on (make test-unit)[https://docs.litellm.ai/docs/extras/contributing_code]
[x] My PR's scope is as isolated as possible, it only solves 1 specific problem

Type

🆕 New Feature

Changes

This Pull Request introduces a new feature to the Grafana dashboard configuration, enabling users to dynamically select the datasource directly within the dashboard. This is achieved by adding a datasource template variable (e.g., $datasource) to the dashboard configuration. Subsequently, the panel configurations that utilize the datasource are updated to reference this template variable.

Before:

After:

Benefits:

Increased Flexibility: Users can now switch between datasources on the dashboard without modifying configuration files, improving adaptability across different environments (development, testing, production).
Improved User Experience: The ability to select datasources via a user-friendly dropdown menu enhances the overall experience.
Simplified Management: This reduces the need to maintain multiple dashboard configurations tailored to specific datasources.

Testing:

Successfully tested the addition of the $datasource template variable on a local Grafana instance.
Verified that dashboard panels correctly display data after selecting different datasources via the template variable.