Add DAG calendar view endpoint

[SavingFrame]

Hello everyone!

This PR adds a new DAG calendar view endpoint that provides scheduling information in a calendar format. This endpoint returns the calendar that existed in Airflow 2.x but provides additional functionality. The new endpoint includes filtering by logical_date and the ability to choose granularity, allowing users to customize their calendar view based on specific time periods and detail levels.

Changes in this PR:

• Create service file that processes historical DagRuns and presumes queued runs
• Add UI endpoint
• Update Swagger documentation
• Add tests for different options of this endpoint

How was this patch tested?

• Added comprehensive unit tests for the calendar endpoint
• Tests cover various scenarios including date filtering, granularity options, and DAG selection
• All existing tests continue to pass
• Static code checks and pre-commit hooks pass

API Details

Endpoint: GET /ui/calendar/{dag_id}

Path Parameters:

• dag_id (string, required): The DAG ID

Query Parameters:

• granularity (string, optional): Time granularity - "hourly" or "daily" (default: "daily")
• logical_date_gte (datetime, optional): Start date for filtering (ISO 8601 format)
• logical_date_lte (datetime, optional): End date for filtering (ISO 8601 format)

Response Format:
Returns an array of CalendarTimeRangeResult objects with the following structure:

[
  {
    "datetime": "2024-01-15 00:00:00",
    "state": "success",
    "count": 5
  },
  {
    "datetime": "2024-01-15 00:00:00",
    "state": "running",
    "count": 2
  },
  {
    "datetime": "2024-01-16 00:00:00",
    "state": "planned",
    "count": 7
  }
]

Response Fields:

• datetime: The timestamp for the calendar entry
• state: Task state - one of "queued", "running", "success", "failed", or "planned"
• count: Number of task instances in this state at the given time

Related Links

• [Discussion](Calendar view in Airflow 3.0? #50907)
• [Reference PR](Delete all old dag pages and redirect to grid view #37988) that provided the main logic
• [Specific changes](https://github.com/apache/airflow/pull/37988/files#diff-917b70d2661fae8322c538a4f60b9d4ba755556036fe0c527eb0411a6ac60f2eL2841)

[boring-cyborg]

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[pierrejeambrun]

Nice, thanks for the pull request.

A few suggestions

[pierrejeambrun]

Just a couple of Nit.

Thanks for the PR, I think it's a good start to iterate on. Since it's a UI endpoint we are free to modify this as we see fit.

[SavingFrame]

Just a couple of Nit.

Thanks for the PR, I think it's a good start to iterate on. Since it's a UI endpoint we are free to modify this as we see fit.

Thank you. Everything is fixed.

[boring-cyborg]

Awesome work, congrats on your first merged pull request! You are invited to check our Issue Tracker for additional contributions.

[pierrejeambrun]

#protm

[bbovenzi]

Great work! As I said in another thread, I love the hourly or daily granularity. I'm excited to make both a monthly and a weekly calendar view.