Let providers handle paging links to enable other paging methods

[mikemahoney218-usgs]

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

We want to move away from limit-offset paging for the data we're serving from Postgres, as deep pages (requiring large offsets) are inefficient and can result in users downloading duplicate records and missing new records if data is appended to an earlier page. We're hoping to move to keyset paging instead, which means users will provide a (non-numeric) key with their queries to get the next page.

Unfortunately limit-offset paging is baked into the itemtypes API here:

pygeoapi/pygeoapi/api/itemtypes.py

Lines 548 to 574 in c976bd7

	if offset > 0:
	prev = max(0, offset - limit)
	content['links'].append(
	{
	'type': 'application/geo+json',
	'rel': 'prev',
	'title': l10n.translate('Items (prev)', request.locale),
	'href': f'{uri}?offset={prev}{serialized_query_params}'
	})
	next_link = False
	if content.get('numberMatched', -1) > (limit + offset):
	next_link = True
	elif len(content['features']) == limit:
	next_link = True
	if next_link:
	next_ = offset + limit
	next_href = f'{uri}?offset={next_}{serialized_query_params}'
	content['links'].append(
	{
	'type': 'application/geo+json',
	'rel': 'next',
	'title': l10n.translate('Items (next)', request.locale),
	'href': next_href
	})

Describe the solution you'd like
Rather than assuming providers are using limit-offset paging, and therefore the last page was always at offset - limit and the next one at offset + limit, it'd be nice if providers could pass their own next links that would skip this entire chunk of code. I think a next link in the response should disable the generation of both prev and next links, as the Features standard mentions that prev links may be skipped based on implementation:

Providing prev links supports navigating back and forth between pages, but depending on the implementation approach it may be too complex to implement.

Describe alternatives you've considered
Potentially each provider should be responsible for implementing a sensible default pagination strategy, but that seems like a much higher lift than assuming (1) the provider is right if it provides a next link (2) the existing strategy can be used otherwise.