Add Erc721 Example (#337)

* Add Erc721 example with ink2.0 syntax

* Remove all println lines

* Remove use dynamic storage

update operator_approvals to <(AccountId, AccountId), bool>

* Remove all none_account related code

* Update author to Parity

* Add ink_prelude declared

* Update owned_tokens_count to AccountId -> u32

* Update tokenId from Hash to TokenId(u32)

* rebase example

* Initial migration to latest ink

* Fix approval

* Move approval

* Remove config file

* Add some tests

* Add more tests

* Patch approve

* Some fixes

* Add docs

* Update examples/erc721/Cargo.toml

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Update examples/erc721/src/lib.rs

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Update examples/erc721/src/lib.rs

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Update examples/erc721/src/lib.rs

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Update examples/erc721/src/lib.rs

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Update examples/erc721/src/lib.rs

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Update examples/erc721/src/lib.rs

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Update examples/erc721/src/lib.rs

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Update docs

* Update examples/erc721/src/lib.rs

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Update examples/erc721/src/lib.rs

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Update examples/erc721/src/lib.rs

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Update examples/erc721/src/lib.rs

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Update examples/erc721/src/lib.rs

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Update examples/erc721/src/lib.rs

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Update examples/erc721/src/lib.rs

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Update examples/erc721/src/lib.rs

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Update examples/erc721/src/lib.rs

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Update examples/erc721/src/lib.rs

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Update examples/erc721/src/lib.rs

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Update examples/erc721/src/lib.rs

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Update examples/erc721/src/lib.rs

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Update examples/erc721/src/lib.rs

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Update examples/erc721/src/lib.rs

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Update examples/erc721/src/lib.rs

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Update examples/erc721/src/lib.rs

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Update examples/erc721/src/lib.rs

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Update examples/erc721/src/lib.rs

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Update examples/erc721/src/lib.rs

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Update examples/erc721/src/lib.rs

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Update examples/erc721/src/lib.rs

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Update examples/erc721/src/lib.rs

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Fix ids

* Update docs

* Update examples/erc721/src/lib.rs

* Update examples/erc721/src/lib.rs

* fix fmt

* fix fmt 2

* fix fmt 3

Co-authored-by: XatMassacrE <xxat.massacre@gmail.com>
Co-authored-by: Hero Bird <robin.freyler@gmail.com>

examples/erc721/.gitignore

+# 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
\ No newline at end of file

examples/erc721/.ink/abi_gen/Cargo.toml

+[package]
+name = "abi-gen"
+version = "0.1.0"
+authors = ["Parity Technologies <admin@parity.io>"]
+edition = "2018"
+publish = false
+
+[[bin]]
+name = "abi-gen"
+path = "main.rs"
+
+[dependencies]
+contract = { path = "../..", package = "erc721", default-features = false, features = ["ink-generate-abi"] }
+ink_lang = { path = "../../../../lang", default-features = false, features = ["ink-generate-abi"] }
+serde = "1.0"
+serde_json = "1.0"

examples/erc721/.ink/abi_gen/main.rs

+fn main() -> Result<(), std::io::Error> {
+    let abi = <contract::Erc721 as ink_lang::GenerateAbi>::generate_abi();
+    let contents = serde_json::to_string_pretty(&abi)?;
+    std::fs::create_dir("target").ok();
+    std::fs::write("target/metadata.json", contents)?;
+    Ok(())
+}

examples/erc721/Cargo.toml

+[package]
+name = "erc721"
+version = "0.1.0"
+authors = ["Parity Technologies <admin@parity.io>"]
+edition = "2018"
+
+[dependencies]
+ink_primitives = { path = "../../primitives", default-features = false }
+ink_abi = { path = "../../abi", default-features = false, features = ["derive"], optional = true }
+ink_core = { path = "../../core", default-features = false }
+ink_lang = { path = "../../lang", default-features = false }
+
+scale = { package = "parity-scale-codec", version = "1.2", default-features = false, features = ["derive"] }
+type-metadata = { git = "https://github.com/type-metadata/type-metadata.git", default-features = false, features = ["derive"], optional = true }
+
+[lib]
+name = "erc721"
+crate-type = [
+	# Used for normal contract Wasm blobs.
+	"cdylib",
+	# Used for ABI generation.
+	"rlib",
+]
+
+[features]
+default = ["test-env"]
+std = [
+    "ink_primitives/std",
+    "ink_abi/std",
+    "ink_core/std",
+    "scale/std",
+    "type-metadata/std",
+]
+test-env = [
+    "std",
+    "ink_lang/test-env",
+]
+ink-generate-abi = [
+    "std",
+    "ink_abi",
+    "type-metadata",
+    "ink_core/ink-generate-abi",
+    "ink_lang/ink-generate-abi",
+]
+ink-as-dependency = []
+
+[profile.release]
+panic = "abort"
+lto = true
+opt-level = "z"
+overflow-checks = true
+
+[workspace]
+members = [
+	".ink/abi_gen"
+]
+exclude = [
+	".ink"
+]