Add `haven` option to `raw_or_label`

[ezraporter]

Description

This PR modifies read_redcap() to let users specify raw_or_label = "haven" and have categorical fields converted to haven_labelled vectors instead of factors. I kept labelled in Suggests and added a check that the user has it installed if they specify raw_or_label = "haven".

Implementation considerations

haven_labelled vectors, unlike factors, preserve the underlying data values/types. The non-trivial part about this is that to apply the labels, the data types in the data must match the data types of the vector of values we read from the metadata. This is slightly tricky because there's no foolproof way to say "cast vector x to type of vector y" for arbitrary y. My approach was to basically do our best at casting using readr's parsing functions and fall back to converting the underlying values to chr if all else fails.

See below for a concrete example if it's helpful.

Proposed Changes

• Add "haven" option to read_redcap() raw_or_label and update appropriate arg checks
• Refactor multi_choice_to_labels()
  • Now takes a raw_or_label argument from read_redcap()
  • Passes off logic for how categorical fields are handled to a label_handler function which will be one of apply_labs_factor() or apply_labs_haven()

Worked Example

Suppose we have a redcap field coded like this:	value	label
3	apple
5	orange
9	banana

The db_data we get from redcap will have a field like this:

 my_field
    <int>
        5
        3
        5
        9

where the int datatype was actually determined by readr since we don't allow users to pass data type specifications to redcap_read_oneshot()

The db_metadata will contain

 field_name   select_choices_or_calculations         
 <chr>        <chr>                                  
 my_field     3, apple | 5, orange | 9, banana

where the values are stored as chr rather than int.

My implementation:

1. Checks the data type of db_data$my_field and finds it's int
2. Casts the labels read from db_metadata, c(apple = "3", orange = "5", banana = "9"), to int with readr::parse_integer()
3. Applies the labels with labelled::set_value_labels()

If step 2 had failed for some reason then it would cast db_data$my_field to chr and apply the labels to that.

Issue Addressed

Related to #178

PR Checklist

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• [x] New/revised functions have associated tests
• [x] New/revised functions that update downstream outputs have associated static testing files (.RDS) updated under inst/testdata/create_test_data.R
• [x] New/revised functions use appropriate naming conventions
• [x] New/revised functions don't repeat code
• [x] Code changes are less than 250 lines total
• [x] Issues linked to the PR using GitHub's list of keywords
• [x] The appropriate reviewer is assigned to the PR
• [x] The appropriate developers are assigned to the PR
• [x] Pre-release package version incremented using usethis::use_version()

Code Review

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Code Review Checklist

• [x] I checked that new files follow naming conventions and are in the right place
• [x] I checked that documentation is complete, clear, and without typos
• [x] I added/edited comments to explain "why" not "how"
• [x] I checked that all new variable and function names follow naming conventions
• [x] I checked that new tests have been written for key business logic and/or bugs that this PR fixes
• [x] I checked that new tests address important edge cases