Add support for more granular rate limit per API route

[spikelu2016]

Is it possible to define rate limits at the granularity of the OpenAI API? I.e., different RPM/TPM for each model? Context is that we want to give 100 students access to the API at the same time through our tier 3 token so every key needs to have 35 RPM/1600 TPM for gpt-3.5-turbo and 50 RPM/5000 TPM for text-embedding-ada-002. If I understand the documentation correctly we could only set the minimum of each limit currently?