006 pagination: Flow PT REST finding

Q Can links.next be trusted to stop, or does the last page lie?

Endpoint GET /entity/versions then follow links.next ; POST /entity/versions/_search ; POST /entity/versions/_summarize

Docs claim links.next is absent on the final page.

Actual

GET /entity/versions?filter[project.Project.id]=N&fields=code&page[size]=100&sort=id,
then follow links.next:

page  1: 100 rows, next=yes
page  2:   0 rows, next=yes
page  3:   0 rows, next=yes
pages 4-31:  0 rows, next=yes  (28 more, identical; the probe cuts the loop at 31)

total rows: 100 over 31 pages

page[size]=30 with explicit page[number]:
  page 1 -> 30 rows, next=yes
  page 3 -> 30 rows, next=yes
  page 4 -> 10 rows, next=yes

asking for a total, one row requested each time:
  GET page[size]=0                        -> 400 {"errors":[{"status":400,"code":103,"title":"Request Parameters invalid.","source":{"page":{"size":["size must be greater than 0"]}},"detail":null}]}
  GET options[return_paging_info]=true    -> 200 keys=['data', 'links'] meta=null links=['next', 'self']
  GET options[include_paging_info]=true   -> 200 keys=['data', 'links'] meta=null links=['next', 'self']
  GET page[totals]=true                   -> 200 keys=['data', 'links'] meta=null links=['next', 'self']
  GET include_count=true                  -> 200 keys=['data', 'links'] meta=null links=['next', 'self']
  GET meta[total]=true                    -> 200 keys=['data', 'links'] meta=null links=['next', 'self']
  POST _search options.return_paging_info -> 200 keys=['data', 'links'] meta=null links=['next', 'self']
  POST _summarize count of id             -> 200 {"summaries": {"id": 100}, "groups": []}

Teaches

links.next is not a terminator: it is present on empty pages too, so "follow next until absent" is an infinite loop. Stop on an empty data array.
Only the stop signal is wrong. Explicit page[number] walks the set, and the short final page returns the remainder.
No total is in a paged read. A GET returns ['data', 'links'] and no meta key, and links holds only self and next, never last. POST _search with options.return_paging_info returns the same two keys.
Five option spellings (options[return_paging_info], options[include_paging_info], page[totals], include_count, meta[total]) are accepted at 200 and change nothing; page[size]=0 is 400 size must be greater than 0.
For "n of N", count with one POST /entity/<type>/_summarize and {"field": "id", "type": "count"}, which returned {"summaries": {"id": 100}} against the 100 rows the walk above found (probe 020).