suggest_orch_frequency doesn't work well for months

[whipson]

If true best orchestrator frequency is a monthly interval (e.g., 1 month, 3 months) suggest_orch_frequency will present this in terms of days (e.g., 31 days, 93 days). This is because we're using a single representation of the number of seconds for a month and not accounting for the fact that months have different amounts of seconds.

This would result in a gradual drifting of the scheduled pipelines.

library(maestro)

test_schedule <- data.frame(
  frequency = c("5 months", "1 quarter"),
  frequency_n = c(5, 1),
  frequency_unit = c("months", "quarter"),
  start_time = as.POSIXct("2024-05-20")
)

suggest_orch_frequency(test_schedule)

#> "31 days"