exposure(
    p::Anniversary,
    from::Date,
    to::Date,
    continued_exposure::Bool = false;
    study_start=typemin(from),
    study_end=typemax(from),
    left_partials::Bool=true,
    right_partials::Bool=true,
)::Vector{NamedTuple{(:from, :to, :policy_timestep),Tuple{Date,Date,Union{Int,Nothing}}}}

Calcualte the exposure periods and returns an array of named tuples with fields:

• from (a Date) is the start date of the exposure interval
• to (a Date) is the end of the exposure interval
• policy_step will either be an Int if an Anniversary or AnniversaryCalendar basis is used, otherwise will be nothing

If continued_exposure is true, then the final to date will continue through the end of the final exposure period. This is useful if you want the decrement of interest is the cause of termination, because then you want a full exposure.

If left_partials or right_partials is set to false, then the exposure will not return partial exposure periods that overlap with the study_start and study_end respectively.

Example

```julia-repl julia> using ExperienceAnalysis,Dates julia> exposure( ExperienceAnalysis.Anniversary(Year(1)), # basis Date(2020,5,10), # issue Date(2022, 6, 10); # termination ) 3-element Vector{NamedTuple{(:from, :to, :policytimestep), Tuple{Date, Date, Int64}}}: (from = Date("2020-05-10"), to = Date("2021-05-09"), policytimestep = 1) (from = Date("2021-05-10"), to = Date("2022-05-09"), policytimestep = 2) (from = Date("2022-05-10"), to = Date("2022-06-10"), policytimestep = 3)

If data has problems like from > to or study_start > study_end throw an error. If the policy doesn't overlap with the study period, return false. If there is overlap, return true.