I'd like to use the `https://api.c3.ai/covid/api/1/linelistrecord/fetch` API but only get 2000 records back. I know that there are more than 2000 records -- how do I get them? 

Here's my code in R:

```
library(tidyverse)
library(httr)
library(jsonlite)

resp <- POST(
  "https://api.c3.ai/covid/api/1/linelistrecord/fetch",
  body = list(
    spec = {}
  ) %>% toJSON(auto_unbox = TRUE),
  accept("application/json")
)

length(content(resp)$objs)

```

I get 2000 records.