sausage-plugin part 2: import! with typed clients (sausage_interface::client_rs), TCP endpoints with rpc.endpoint, examples

Part 1 fixes: complete stdout writes, buffered stdin, Rust type names
in schemas, enum variant docs, -32603 for serde errors in handlers,
crate docs and modules. End-to-end check of a generated consumer through
a fake core.

interface/tests/client.rs

@@ -0,0 +1,16 @@
+//! Check the shared generator against a real example's discovered document.
+#[test]
+fn notes_client_preserves_names_and_docs() {
+    let document =
+        serde_json::from_str(include_str!("../../examples/consumer/imports/notes.json")).unwrap();
+    let code = sausage_interface::client_rs("notes", &document).unwrap();
+    assert!(code.contains("pub struct AddParams"));
+    assert!(code.contains("pub struct Added"));
+    assert!(!code.contains("AddedResult"));
+    assert!(code.contains("The complete note text"));
+    assert!(code.contains("pub fn add(params: AddParams)"));
+    syn::parse_file(&code).unwrap();
+    let target = std::path::Path::new(env!("CARGO_MANIFEST_DIR")).join("../target/sdk");
+    std::fs::create_dir_all(&target).unwrap();
+    std::fs::write(target.join("notes-client.rs"), code).unwrap();
+}