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.

sdk/macros/Cargo.toml

@@ -8,6 +8,8 @@ description = "Macros of the Sausage plugin SDK. Use them through `sausage-plugi
 proc-macro = true
 
 [dependencies]
+sausage-interface = { path = "../../interface" }
+serde_json = "1"
 syn = { version = "2", features = ["full"] }
 quote = "1"
 proc-macro2 = "1"