Standardize response schemas for variables and xcoms in Execution API

[rjgoyln]

Description

Currently, the Execution API has inconsistent response formats for success messages. While endpoints like connections.py return well-defined Pydantic schemas (e.g., ConnectionResponse), others like variables.py and xcoms.py return raw Python dictionaries (e.g., {"message": "..."}).

Returning raw dictionaries causes the OpenAPI specification to default to Any or object, which makes it difficult to generate strongly-typed SDKs and Clients.

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[SameerMesiah97]

Looks fine. I have left a few comments.

One thing, I’m a bit surprised tests haven’t been adjusted for this. Since this changes the response model and DELETE status from 204 to 200, I would have expected some assertions around return values and/or status codes to be updated. Have you run the relevant unit tests locally?

[SameerMesiah97]

You might need to specify a return type here like this to satisfy MyPy:

-> MessageResponse

[SameerMesiah97]

I would explicitly set the status code here like this:

status_code=status.HTTP_200_OK

[rjgoyln]

Thanks your advise!!

[potiuk]

@rjgoyln This PR has been converted to draft because it does not yet meet our Pull Request quality criteria.

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