[MCC-140732] Feature/better index

Fixes the filtered index by status, adds specs, begins the refactoring of the big spec file by pulling things out into a specific drd_index_spec.rb file.

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Finished in 56.38 seconds (files took 0.64189 seconds to load)
19 examples, 0 failures, 1 pending

Randomized with seed 10197
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