Fix for job tasks to be sorted by task kay alphabetically

[goda]

Fix for #286 - adding a method in Job class that sorts its tasks by task_key whenever the class is serialized. This will ensure that when no job task's have been changed that terraform doesn't think an update is needed.

[osoucy]

Can you update the CHANGELOG.md file to include in the updated section:
* Jobto automatically alphabetically sortstasks [[#286](https://github.com/okube-ai/laktory/issues/277)]

[osoucy]

Can you update the test_job.py file by changing the order of the tasks in the job definition ? This will validate that the new sorting works as expected. Final job definition could be something like:

job = Job(
    name="job-stock-prices",
    clusters=[
        {
            "name": "main",
            "spark_version": "14.0.x-scala2.12",
            "node_type_id": "Standard_DS3_v2",
        },
    ],
    tasks=[
        {
            "depends_ons": [{"task_key": "ingestion"}],
            "pipeline_task": {"pipeline_id": "${resources.pl-spark-dlt.id}"},
            "task_key": "pipeline",
        },
        {
            "task_key": "view",
            "sql_task": {
                "query": {"query_id": "456"},
                "warehouse_id": "123",
            },
        },
        {
            "job_cluster_key": "main",
            "notebook_task": {
                "notebook_path": "job/ingest_stock_prices",
            },
            "task_key": "ingestion",
        },
    ],
    email_notifications={
        "on_duration_warning_threshold_exceededs": ["[email protected]"],
        "on_failures": ["[email protected]"],
        "on_starts": ["[email protected]"],
        "on_successes": ["[email protected]"],
    },
)

[goda]

Pushed new commit with the requested changes:

• CHANGELONG.md updated to reflect the change
• Changed order of tasks in test_job job object to ensure the sorting of the tasks works
• Moved the sort_tasks method right after the attribute declarations in Job class