HDI?

Would it be in the scope of posterior to provide support for HDI's in contrast with quantile-based intervals? For example, say I wanted to quickly summarize my draws by their modes and 95% intervals.

example_draws() %>% 
  summarise_draws(mode = Mode, ~ quantile(.x, probs = c(.025, .975)))

# A tibble: 10 × 4
   variable  mode  `2.5%` `97.5%`
   <chr>    <dbl>   <dbl>   <dbl>
 1 mu        5.91  -2.16     10.2
 2 tau       1.74   0.174    14.6
 3 theta[1]  5.67  -2.81     22.7
 4 theta[2]  5.44  -3.24     14.9
 5 theta[3]  5.52 -15.0      13.2
 6 theta[4]  5.94  -4.64     14.8
 7 theta[5]  4.26  -8.68     12.3
 8 theta[6]  3.20  -6.80     12.8
 9 theta[7]  4.46  -2.57     18.1
10 theta[8]  4.22  -6.53     14.8

There's great support for percentile-based intervals. Is there support for HDI's?

Start with the existing summarise_draws usage and the percentile-based interval support referenced in the issue. Determine how an HDI interval and mode summary should fit the requested output, then verify the result against the example draws. The issue names no file or test, so locating the relevant implementation and defining the expected behavior are part of the work.