paging and next links

[matthewhanson]

sat-api uses the parameters page and limit when the number of Items is more than limit.

This is not compliant with STAC because STAC doesn't specify a mechanism to do paging. The assumption is that all results will be returned, although this can cause errors with sat-api when there are more than around 920 items (sat-utils/sat-search#69)

See the STAC issue discussing this:
radiantearth/stac-spec#381

Currently the next links are formed by convert the POST parameters to a GET request. However there are two issues:

• for large geometries the payload size may end up being larger than what is allowed for GET.
• objects are not correctly encoded to JSON anyway. If I make a POST request the intersects parameter is not deserialized, e.g.,
  https://sat-api.developmentseed.org/stac/search?intersects=%5Bobject%20Object%5D&page=2&limit=10

cc @vincentsarago @sharkinsspatial

[matthewhanson]

The page parameter is compliant starting with STAC 0.7.0, so this part is fine. However, the next link still needs to stringify the JSON.