Document the trust model and panics in the codebase.

Signed-off-by: Piotr Sikora <[email protected]>

DEVELOPMENT.md

@@ -1,5 +1,14 @@
 # Development
 
+## Proxy-Wasm ABI compliance & trust model
+
+It is expected that the host environment is completely trusted and compliant
+with the [Proxy-Wasm ABI specification] (currently v0.2.1).
+
+This means that receiving unexpected callback, status, lifecycle flow and/or
+incorrectly serialized parameters is considered a permanent failure and will
+result in a `panic`.
+
 ## Testing
 
 GitHub Actions can be executed locally using the [`act`] tool.
@@ -28,5 +37,6 @@ bazelisk run //bazel/cargo:crates_vendor -- --repin all
 ```
 
 
+[Proxy-Wasm ABI specification]: https://github.com/proxy-wasm/spec
 [`act`]: https://github.com/nektos/act
 [`bazelisk`]: https://github.com/bazelbuild/bazelisk