fix header case handling and support twisted >=24.10

[thrau]

Motivation

In twisted/twisted#12264, the internal API for header case handling was significantly refactored. Rolo was modifying twisted internals to implement a raw header casing mode, which then broke.

This PR creates a backwards compatible change, that will work with twisted >24 (both pre- and post- refactor versions).

Discussion

The PR introduces a new Header subclass that implements its own case handling. The main motivation for twisted/twisted#12264 was performance of header encoding, an issue we don't have since we don't actually do any encoding of headers in raw header mode.

The drawback of this new class is that HeaderPreservingHTTPChannel and HeaderPreservingWSGIResponse are no longer compatible with the default twisted request object. This actually surfaced because the way the requestFactory was passed was also changed, and until I added it explicitly to serve_twisted_websocket_listener, the tests would fail.
Anyway, I think it's OK, since no one really instantiates manually a Site object for serving rolo routers, and for serving Gateway instances we already have the documented TwistedGateway(Site) which configures the Site object correctly.

I also removed the copying of the default _caseMappings, since it wasn't doing anything. Their values were always overwritten by HeaderPreservingHTTPChannel.headerReceived, and HeaderPreservingWSGIResponse.startResponse anyway.

Changes

• Rolo now supports twisted >=24.10

[thrau]

I've also released localstack-twisted 25.5.0 which can be upgraded together with rolo in localstack

[bentsku]

Nice, LGTM! Thanks for tackling this, this is a neat fix and is more understandable 👍 thanks for also making it backward compatible. Looks awesome!

I'll create a new 0.8.0 release with all of this 👍