Enabled caching and RateLimitMiddleware duplicate all Ratelimt-* headers in response

[mikhail-tokarev]

Description

with litestar.middleware.rate_limit.RateLimitMiddleware added to app middleware and cache=True enabled on route handler you can observe duplicates for all Ratelimit-* response headers like this:

URL to code causing the issue

No response

MCVE

from litestar import Litestar, MediaType, get
from litestar.middleware.rate_limit import RateLimitConfig

rate_limit_config = RateLimitConfig(rate_limit=("minute", 1), exclude=["/schema"])

@get("/", cache=True, media_type=MediaType.TEXT, sync_to_thread=False)
def handler() -> str:
    return "ok"

app = Litestar(route_handlers=[handler], middleware=[rate_limit_config.middleware])

Steps to reproduce

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Screenshots

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Logs

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Litestar Version

2.9.1

Platform

• Linux
• Mac
• Windows
• Other (Please specify in the description above)

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