feat(workflow): add LambdaTask builder for TaskType.LAMBDA

Closes #427

TaskType.LAMBDA existed in the enum but had no builder class, so LAMBDA tasks
could only be constructed from raw dicts via the Python SDK. Add a LambdaTask
builder that mirrors InlineTask: it sets scriptExpression from the script
argument and merges any bindings into input_parameters.

Signed-off-by: rahul188 <rahulkuchhadia@gmail.com>

Author: rahul188

src/conductor/client/workflow/task/lambda_task.py

@@ -0,0 +1,19 @@
+from __future__ import annotations
+from typing import Dict, Optional
+from typing_extensions import Self
+
+from conductor.client.workflow.task.task import TaskInterface
+from conductor.client.workflow.task.task_type import TaskType
+
+
+class LambdaTask(TaskInterface):
+    def __init__(self, task_ref_name: str, script: str, bindings: Optional[Dict[str, str]] = None) -> Self:
+        super().__init__(
+            task_reference_name=task_ref_name,
+            task_type=TaskType.LAMBDA,
+            input_parameters={
+                "scriptExpression": script,
+            }
+        )
+        if bindings is not None:
+            self.input_parameters.update(bindings)

tests/unit/workflow/test_lambda_task.py

@@ -0,0 +1,26 @@
+from conductor.client.workflow.task.lambda_task import LambdaTask
+from conductor.client.workflow.task.task_type import TaskType
+
+SCRIPT = "(function(){ return {out: $.x + 1}; })()"
+
+
+def test_lambda_task_builds_script_expression():
+    task = LambdaTask(task_ref_name="lambda_ref", script=SCRIPT)
+    assert task.task_reference_name == "lambda_ref"
+    assert task.input_parameters == {"scriptExpression": SCRIPT}
+
+    workflow_task = task.to_workflow_task()
+    assert workflow_task.type == TaskType.LAMBDA.value
+    assert workflow_task.input_parameters["scriptExpression"] == SCRIPT
+
+
+def test_lambda_task_merges_bindings():
+    task = LambdaTask(
+        task_ref_name="lambda_ref",
+        script=SCRIPT,
+        bindings={"x": "${workflow.input.x}"},
+    )
+    assert task.input_parameters == {
+        "scriptExpression": SCRIPT,
+        "x": "${workflow.input.x}",
+    }