Consider disallowing redirects for API requests that redirect from POST to GET

[philvarner]

I recently had a situation where a server that used an https URL incorrectly had http links in it's link relations. The result of this was that the underlying http client library in pystac-client got a redirect from a POST /search request, and then retried with a GET /search request. However, this didn't work correctly, since the POST body was not also re-constructed as GET query parameters, so the search instead resulted in all items being returned.

1. Changing the default behavior of redirects like this would be difficult to do outside of a major release.
2. Adding some documentation about ensuring that the response link rels match the requested URL could be useful.