feat(ownable): implement trait

An attepmt of re-implementing `Ownable.sol` from the Open Zeppelin directly in ink!

smart-contracts/contracts/tko_interfaces/.gitignore

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+# Ignore build artifacts from the local tests sub-crate.
+/target/
+
+# Ignore backup files creates by cargo fmt.
+**/*.rs.bk
+
+# Remove Cargo.lock when creating an executable, leave it for libraries
+# More information here http://doc.crates.io/guide.html#cargotoml-vs-cargolock
+Cargo.lock

smart-contracts/contracts/tko_interfaces/Cargo.toml

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+[package]
+name = "tko_interfaces"
+version = "0.1.0"
+authors = ["[your_name] <[your_email]>"]
+edition = "2018"
+
+[dependencies]
+ink_primitives = { version = "3.0.0-rc3", default-features = false }
+ink_metadata = { version = "3.0.0-rc3", default-features = false, features = ["derive"], optional = true }
+ink_env = { version = "3.0.0-rc3", default-features = false }
+ink_storage = { version = "3.0.0-rc3", default-features = false }
+ink_lang = { version = "3.0.0-rc3", default-features = false }
+
+scale = { package = "parity-scale-codec", version = "2.1", default-features = false, features = ["derive"] }
+scale-info = { version = "0.6.0", default-features = false, features = ["derive"], optional = true }
+
+[lib]
+name = "tko_interfaces"
+path = "lib.rs"
+crate-type = [
+	# Used for normal contract Wasm blobs.
+	"cdylib",
+]
+
+[features]
+default = ["std"]
+std = [
+    "ink_metadata/std",
+    "ink_env/std",
+    "ink_storage/std",
+    "ink_primitives/std",
+    "scale/std",
+    "scale-info/std",
+]
+ink-as-dependency = []

smart-contracts/contracts/tko_interfaces/access.rs

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+use ink_lang as ink;
+use ink_env::AccountId;
+
+#[ink::trait_definition]
+pub trait IsOwnable {
+    // fn initialize(&mut self);
+    //
+    // #[ink(message)]
+    // fn owner(&self) -> Option<Address>;
+    //
+    // #[ink(message)]
+    // fn renounce_ownership(&mut self) {
+    //     self._only_owner();
+    //     self._set_owner(None);
+    // }
+    //
+    // #[ink(message)]
+    // fn transfer_ownership(&mut self, new_owner: Address) {
+    //     self._only_owner();
+    //     self._set_owner(Some(new_owner));
+    // }
+
+    /// Tells if the message sender is the owner
+    #[ink(message)]
+    fn owner(&self) -> AccountId;
+    // fn _only_owner(&self) {
+    //     match self.owner() {
+    //         Some(owner) => assert!(owner == self.message_sender(), "Ownable: caller is not the owner"),
+    //         None =>  panic!("Ownable: caller is not the owner")
+    //     }
+    // }
+    //
+    // fn _set_owner(&mut self, new_owner: Option<Address>);
+
+    // fn _message_sender(&self) -> Address;
+}

smart-contracts/contracts/tko_interfaces/lib.rs

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+pub mod access;