Spin 4.0

[itowlson]

Work in progress! I've put the initial "fork all the things" stuff in the initial commit so in principle you can review the boilerplate for boilerplatey things and the content changes for actual content separately, but I dunno, maybe I should make two separate PRs, anyway, v4, WIP.

File	Changes	Status (I think)
api-guides-overview.md	Noted asyncness - need to confirm which APIs we are asyncifying this is looking settled, revisit if it changes	Completed
build.md	Build profiles - added	Completed
cache.md	None	Completed
cli-reference.md	Regenerate when Spin 4 stabilises	Pending v4 readiness
contributing-docs.md	None	Completed
contributing-spin.md	None	Completed
deploying.md	Remove Fermyon Cloud	Completed
distributing-apps.md	Build profiles - added	Completed
dynamic-configuration.md	None	Completed
extending-and-embedding.md	None	Completed
go-components.md	Go SDK WIP, wrote up inbound HTTP but foundered on outbound and other stuff	Started
http-outbound.md	http_service-fied Rust. Streaming outbound reqs/resps in Rust - done (check once SDK lands). TODO: Go, JS, Python.	Started
http-trigger.md	Instance reuse - added. http_service - added.	Started
index.md	None	Completed
install.md	None	Completed
javascript-components.md	TBA
kv-store-api-guide.md	Asyncified Rust. TODO: JS, Python, Go	Started
language-support-overview.md	No changes	Completed
managing-plugins.md	None	Completed
managing-templates.md	None	Completed
manifest-reference.md	Build profiles - added	Completed
mqtt-outbound.md	Asyncified Rust. TODO: JS, Python, Go	Started
observing-apps.md	None I think (wasi-http isn't asyncified yet)	Completed
other-languages.md	No v4-related changes although we should look at this for retirement or for Kotlining	Completed
plugin-authoring.md	None	Completed
python-components.md	TBA
quickstart.md	Removed Fermyon Cloud stuff (do we want to talk more about deploying here? I added a link to the deployment options page). Asyncified Rust. TODO: JS, Python, Go.	Started
rdbms-storage.md	PG only is now async/streaming	Completed
redis-outbound.md	Asyncified Rust. TODO: JS, Python, Go	Started
redis-trigger.md	Async entry point, renamed Rust attribute. TODO: Python, Go SDKs (JS doesn't do Redis)	Started
running-apps.md	Nothing to do here?	Completed
rust-components.md	Asyncified, derouterised, de-http-crated. Need to verify that the SDK accepts borrows but basically	Completed
see-what-people-have-built-with-spin.md	None	Completed
serverless-ai-api-guide.md	Asyncify HTTP context stuff, no change to LLM API. Done for Rust. TODO: JS, Python, Go	Started
spin-application-structure.md	Changed http_component to http_service. Revisit once template and response body stuff is sorted.
sqlite-api-guide.md	Asyncified Rust HTTP bits. Need to nail down wrappers. TODO: JS, Go, Python	Started
template-authoring.md	None	Completed
testing-apps.md	We believe this doesn't work with P3. Removing for now	Done
triggers.md	I don't think there are any changes here	Completed
troubleshooting-application-dev.md	Remove spin test reference until we can work on that	Done
upgrade.md	None	Completed
variables.md	Async, http_service, response guff: Rust done. TODO: JS, Go, Python	Started
writing-apps.md	Just some asyncifying I think	Completed

General things:

• Updated remaining wasm32-wasip1 to wasm32-wasip2
• TODO: Change TinyGo titles/references to BigGo (TBC)
• TODO: I just realised I need to cover off bindgen-level futures and stream APIs. Fie!

[itowlson]

@fibonacci1729 I think this is about as ready as I can get it for now - still have Go/JS/Python changes to make once those are ready, and a few possible changes to the Rust SDK as we discussed. Let me know if you see / can think of anything else that needs to change!