AIP-84: Migrating GET queued asset events for DAG to fastAPI

[amoghrajesh]

related: #42370

Migrating the GET queued asset events for a DAG endpoint to fast API.

Setup:

1. Created producer and consumer dags:
   

2. Paused one producer while running the other to generate queued events
   

Responses:

1. Legacy
   

2. FastAPI
   

With time filtering:

1. Legacy
   

(Beyond creation time)

2. FastAPI
   

(Beyond creation time)

Swagger spec: (maintained under dag section)

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[pierrejeambrun]

A few suggestions

[amoghrajesh]

@pierrejeambrun FYI, I have pushed the changes for all the "resolved" comments. The rest are open for input from you.

EDIT: I kept the endpoint at public/dags.py cos if I move to assets, the path will become: /public/assets/{dag_id}/assets/queuedEvent due to the underlying router registration. I moved the datamodels and tests to assets.py however

[pierrejeambrun]

Small suggestions / questions almost ready

[pierrejeambrun]

As many of other PRs depends on this one, to try to make them move forward I added a few commits, I think it's ready