feat(papi): Add a container crate

Cargo.toml

@@ -1,5 +1,5 @@
 [workspace]
-members = ["src/api", "src/declarations/cycles_ledger", "src/example/app_backend", "src/example/paid_service", "src/example/paid_service_api", "src/guard"]
+members = ["src/api", "src/declarations/cycles_ledger", "src/example/app_backend", "src/example/paid_service", "src/example/paid_service_api", "src/guard", "src/papi"]
 resolver = "2"
 
 [workspace.dependencies]

USAGE.md

@@ -0,0 +1,7 @@
+# Usage
+
+## Creating a paid API
+
+### Accept many payment types
+- In your canister, you need to decide which payment types you wish to accept.  In [this example](./src/example/paid_service/src/state.rs) a `PAYMENT_GUARD` is defined that accepts a variety of payment options.
+- In the API methods, you need to [deduct payment](./src/example/paid_service/src/lib.rs) before doing work.

src/example/paid_service/src/lib.rs

@@ -40,7 +40,7 @@ async fn cost_1b_icrc2_from_caller() -> Result<String, PaymentError> {
     Ok("Yes, you paid 1 billion cycles!".to_string())
 }
 
-/// An API method that requires 1 billion cycles.
+/// An API method that requires 1 billion cycles, paid in whatever way the client chooses.
 #[update()]
 async fn cost_1b(payment: PaymentType) -> Result<String, PaymentError> {
     let fee = 1_000_000_000;

src/papi/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "ic-papi"
+version = "0.1.0"
+edition = "2021"
+description = "Library for implementing Paid APIs on the Internet Computer"
+
+[dependencies]
+ic-papi-api = { workspace = true }
+ic-papi-guard = { workspace = true }

src/papi/src/lib.rs

@@ -0,0 +1,2 @@
+pub use ic_papi_api as api;
+pub use ic_papi_guard as guard;