Get the provider roster-size spread per country

How Access Point provider roster sizes are spread in each country, in one call. A roster size is the number of participant IDs one provider serves in the country (country_roster of GET /v1/aps?country=). Each country row is the five-number summary over the providers with at least one participant there: n providers, min, q1, median, q3, max, and total (the sum). Quantiles use linear interpolation between the two closest ranks (type 7), rounded to 2 decimals.

points is every roster size in ascending order when the country has fewer than points_max providers, and null at or above it. The response carries sizes only, no provider key or name. Countries are ordered by median, largest first. A summary of a country with few providers says little: the console does not draw a country with fewer than 8.