feat: add transfer_ownership (#1193)

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Time spent on this PR: 0.1 day

## Pull request type

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Please check the type of change your PR introduces:

- [ ] Bugfix
- [x] Feature
- [ ] Code style update (formatting, renaming)
- [ ] Refactoring (no functional changes, no api changes)
- [ ] Build related changes
- [ ] Documentation content changes
- [ ] Other (please describe):

## What is the current behavior?
Ownership of the Kakarot contract can't be transfered.
<!-- Please describe the current behavior that you are modifying,
or link to a relevant issue. -->

Resolves #1192 

## What is the new behavior?
- Add transfer of ownership of the contract.
- Add tests.

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src/kakarot/kakarot.cairo

@@ -10,7 +10,7 @@ from starkware.cairo.common.math_cmp import is_not_zero
 from starkware.cairo.common.uint256 import Uint256
 from starkware.starknet.common.syscalls import get_caller_address, replace_class, get_tx_info
 from starkware.cairo.common.registers import get_fp_and_pc
-from openzeppelin.access.ownable.library import Ownable
+from openzeppelin.access.ownable.library import Ownable, Ownable_owner
 
 // Local dependencies
 from backend.starknet import Starknet
@@ -55,6 +55,22 @@ func upgrade{syscall_ptr: felt*, pedersen_ptr: HashBuiltin*, range_check_ptr}(
     return ();
 }
 
+// @notive Returns the owner of the contract
+@external
+func get_owner{syscall_ptr: felt*, pedersen_ptr: HashBuiltin*, range_check_ptr}() -> (owner: felt) {
+    return Ownable_owner.read();
+}
+
+// @notive Transfer the ownership of the contract
+// @param new_owner The new owner
+@external
+func transfer_ownership{syscall_ptr: felt*, pedersen_ptr: HashBuiltin*, range_check_ptr}(
+    new_owner: felt
+) {
+    Ownable.transfer_ownership(new_owner);
+    return ();
+}
+
 // @notice Set the native token used by kakarot
 // @dev Set the native token which will emulate the role of ETH on Ethereum
 // @param native_token_address The address of the native token

tests/end_to_end/test_kakarot.py

@@ -16,6 +16,7 @@
     hex_string_to_bytes_array,
 )
 from tests.utils.reporting import traceit
+from tests.utils.syscall_handler import SyscallHandler
 
 params_execute = [pytest.param(case.pop("params"), **case) for case in test_cases]
 
@@ -392,3 +393,27 @@ async def test_should_upgrade_class_hash(
             assert prev_class_hash != new_class_hash
             assert new_class_hash == class_hashes["replace_class"]
             await invoke("kakarot", "upgrade", prev_class_hash)
+
+    class TestTransferOwnership:
+        @SyscallHandler.patch("Ownable_owner", 0xDEAD)
+        async def test_should_raise_when_caller_is_not_owner(
+            self, kakarot, invoke, other
+        ):
+            prev_owner = await kakarot.functions["get_owner"].call()
+            try:
+                await invoke("kakarot", "transfer_ownership", account=other)
+            except Exception as e:
+                print(e)
+            new_owner = await kakarot.functions["get_owner"].call()
+            assert prev_owner == new_owner
+
+        @SyscallHandler.patch("Ownable_owner", SyscallHandler.caller_address)
+        async def test_should_transfer_ownership(self, kakarot, invoke, other):
+            prev_owner = (await kakarot.functions["get_owner"].call()).owner
+            await invoke("kakarot", "transfer_ownership", other.address)
+            new_owner = (await kakarot.functions["get_owner"].call()).owner
+
+            assert prev_owner != new_owner
+            assert new_owner == other.address
+
+            await invoke("kakarot", "transfer_ownership", prev_owner, account=other)