Import series in Calc (Libre Office)

Related to #626 (closed)

Description

As a user, I want to import data series from DBnomics into a specific sheet of Calc.

Calc accepts URLs to CSV files (Sheet>Link to external data).

It should be possible to add a DBnomics link in the Sheet menu of Calc, then Link to External Data.

It can't be done easily now because through the Download button in DBnomics, the link we have doesn't have ".csv" as endpoint.

Tasks

• UI: modify the dropdown menu as described below in UX section
• API: modify the URLs to end with .csv and .xslx instead of parameter format=
• LibreOffice Calc: check that CSV import is possible
• Improve limit of 1000 series (cf section below)
• Document the feature in dbnomics-docs (preferably in the FAQ), with a link to the "Link to External Data" (Calc Help)
• Fix regression where dimensions are ignored

UX

New dropdown menu

- Excel: [download] [copy URL]
- CSV: [download] [copy URL]
- JSON: [copy URL]

where [download] is a link to an API URL, and [copy URL] is a button styled like a link.

The groups "Tabular files" and "Programming languages" would be removed.

Note: the copy URL feature is already implemented for JSON.

Limit of 1000 series

Rather than truncating the file to 1000 series max, which can be misleading if the user is not aware of it, I propose to gray the Download button (or the buttons in the menu) and force the user to add filters until the number of results (series found) is <= 1000.

Currently the warning is not clear. Currently the warning is not clear.