Add `pageSize` for offline downloads API (occurrences/offline/download)

[adam-collins]

1. Add pageSize for offline downloads API

Request to add pageSize to offline downloads API to enable galah users to check result output before downloading all records. (Chat thread on Slack if further info required)

requested by @mjwestgate

2. Update to API docs

The API docs on Swagger show additional arguments that do not work for occurrences/offline/download. These should be removed to avoid confusion.

These arguments include dir but there may be others.

[adam-collins]

The intended use is to preview results. Some considerations.

• There should be a configurable limit on the maximum number of records permitted in the preview. e.g. 5.
• DOI should not be minted when previewing.
• email notifications should be disabled for previews.
• logging of a download request should be disabled.
• The generated citation can remain.
• The generated header file should remain.
• A new webservice is unnecessary. The download service throttles to one request at a time per user.

Any additional thoughts @djtfmartin ?

[adam-collins]

The provided pageSize must differ from the default pageSize of 10

[djtfmartin]

@adam-collins I am wondering if this requirement would be better served with a newer version (v2) of the /occurrence/search JSON API that returned the full darwin core record - which would be closer to the set of fields in download.

Currently the /occurrences/search just returns a small number of fields that where there to just support the UI - not very useful as a general application.

@mjwestgate how does this sound ?

this is probably just a different way of thinking of it, but i've thought for some time that we would have a better JSON occurrence search service that allowed access to a bigger range of the fields indexed.

[adam-collins]

I agree and am not aware of any discussion. No changes required. Closing.