Support customizing “Accept” header

[roycaihw]

What is the feature and why do you need it:
From a conversation in slack. Kubernetes client-go has a metadata client that only retrieves object metadata from the API server. It helps in scenarios where the user only cares about object metadata and wants to reduce the client-side deserialization time. The easiest way to support this feature in the Python client is to do it in the dynamic client.

Describe the solution you'd like to see:
The dynamic client hard-codes the Accept header. We can have a new parameter to allow overwriting the value like how the metadata client does:

SetHeader("Accept", "application/vnd.kubernetes.protobuf;as=PartialObjectMetadata;g=meta.k8s.io;v=v1,application/json;as=PartialObjectMetadata;g=meta.k8s.io;v=v1,application/json").

The solution should be e2e tested.

[roycaihw]

/help

cc @Yashks1994 @Priyankasaggu11929

[k8s-ci-robot]

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In response to this:

/help

cc @Yashks1994 @Priyankasaggu11929

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[Yashks1994]

/assign

[Yashks1994]

Opened a PR- kubernetes-client/python-base#236 to accept the header.

[roycaihw]

@Yashks1994 Could you run https://github.com/kubernetes-client/python/blob/master/devel/submodules.md#update-submodule to update the submodule, so that kubernetes-client/python-base#236 is included in the main repo?