feat: check header for pagination if plugin requires it

[ValentinaHutter]

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[ValentinaHutter]

I have been working on a plugin for the CMR api, which supports pagination via a CMR-Search-After value in the request header. In order to support this option, I added a next_page_token_location value in the code and put it into my providers.yaml:

   search: !plugin
    type: CMRSearch
    api_endpoint: "https://cmr.earthdata.nasa.gov/search/"
    ...
    pagination:
      next_page_token_location: header
      next_page_token_key: cmr_search_after

As this update might be useful for other plugins, where pagination is handled through the header, I added the code in this PR.
In my example, the plugin query function will then receive a cmr_search_after parameter, which can be used to handle pagination internally.