Document and rationalise worker interface

[richfitz]

• document the rrq_worker class
• export the script writer
• export the "worker from config"

This became necessary when writing the docs

[codecov]

Codecov Report

Merging #48 (4908293) into master (ad0b195) will not change coverage.
The diff coverage is 100.00%.

❗ Current head 4908293 differs from pull request most recent head 05817e8. Consider uploading reports for the commit 05817e8 to get more accurate results

@@            Coverage Diff            @@
##            master       #48   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           24        24           
  Lines         1667      1666    -1     
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- Hits          1667      1666    -1     

Impacted Files	Coverage Δ
R/configure.R	100.00% <ø> (ø)
R/dependencies.R	100.00% <100.00%> (ø)
R/keys.R	100.00% <100.00%> (ø)
R/progress.R	100.00% <100.00%> (ø)
R/worker.R	100.00% <100.00%> (ø)
R/worker_messages.R	100.00% <100.00%> (ø)
R/worker_run.R	100.00% <100.00%> (ø)
R/worker_runner.R	100.00% <100.00%> (ø)
R/worker_spawn.R	100.00% <100.00%> (ø)

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[r-ash]

This looks good, small typo I noticed.

Is moving most of the variables in the worker to private just for a cleaner interface to users? Honestly the functions being called with private looks a bit funny to me (and self but to a lesser extent). Feels like if those properties need to be accessed then they should be available as public properties. I see why though, I think none of the functions which take private are called from outside the function? So really just using it as a way to break up the code in the object. Perhaps that suggests though that the object is managing too many concerns and it might be worth breaking it up into several objects. At least that is what you would have to do in something like java but perhaps because we can pass around private it is fine - the code isn't difficult to understand. I think fine as is but maybe something to discuss as a general pattern.