🚀 What's the Problem?

Hi!

The current metrics sent by openLit for the gen_ai component do not allow grouping by tag. It could be a good idea to introduce custom tags to enable monitoring by group. For example, my application manages many clients simultaneously, and all the cost monitoring metrics allow me to see the total cost spent by my application, but only per model (as my application uses several LLM models).

It would be very useful to be able to define additional custom tags for the metrics, configurable via sdk.
In my case, I would add the client ID, so I could monitor costs for individual user (and total cost as well).