https://docs.rs/stylus-sdk/0.8.1/stylus_sdk/abi/trait.Router.html#tymethod.receive https://docs.rs/stylus-sdk/0.8.1/stylus_sdk/abi/trait.Router.html#tymethod.fallback Introduced in SDK 0.7.0: https://github.com/OffchainLabs/stylus-sdk-rs/releases/tag/v0.7.0
