format_api_dates for requests without seconds

Figure out best way to deal with no-seconds in `format_api_dates`


```r
lubridate::as_datetime("2010-01-01T00:00Z")
[1] "2020-10-01 01:00:00 UTC" 
lubridate::as_datetime("2014-05-01T00:00Z") 
[1] NA Warning message: All formats failed to parse. No formats found.
```
