[Request] Add Flex pricing option for o3 and o4-mini OpenAI models

[GitGoppy]

🥰 Feature Description

Write an option to support using flex pricing for o3 and o4-mini at OpenAI.
Flex pricing is half the price for input and output tokens at the price of speed of response from the AI or resource unavailable errors during peak usage of the models.

🧐 Proposed Solution

This should be a special feature for these models (o3 and o4-mini and more to come) similar to Effort adjustment in Agent settings. that sets the api option service_tier="flex" in response part of the OpenAI api. It is described https://platform.openai.com/docs/guides/flex-processing in this link

📝 Additional Information

This might cause timeout errors due to timeout delay, can be mitigated by turning on "Client side fetching" for OpenAI platform in platform settings.

[lobehubbot]

👀 @GitGoppy

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