Add a group to one df based on values from another df

Question

I have two df\'s:

df_1 <- 
  tribble(
    ~time, ~v1, ~v2,
    -3,  213,  1,
    -2, 124,  4,
    -1,  532,  2,
    0,  423,  5,
    -3,  123, 3,
    -2,