Improve docs for HeaderApiVersionReader

[voroninp]

Is there an existing issue for this?

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Is your feature request related to a problem? Please describe the problem.

I believe it's important to properly manage expectations. As HeaderApiVersionReader has a default constructor, one may expect there is a default header. And this is not true. It's better to be explicit about what is required for the class to perform its duties.

Describe the solution you'd like

While completely removing default constructor would be a breaking change, I believe it's worth adding xmldoc remarks, explaining that HeaderNames must be initialized.

Additional context

No response