Rework ability_spec.rb so it doesn't spill over into other specs

[jrhoads]

Purpose

Isolate ability spec so that it does not affect other specs in the suite.

Approach

Remove before(:all) and after(:all) blocks and replace them with localized let statements that adhere to transactions and auto-delete whenever the individual test is finished.

Many tests have been consolidated in to larger blocks to limit the number of times a DB call must be made.

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)

• [ ] New feature (non-breaking change which adds functionality)

• [ ] Breaking change (fix or feature that would cause existing functionality to change)

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• Consider using positive language as opposed to neutral when offering feedback. This is to avoid the negative bias that can occur with neutral language appearing negative.
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