SE-3083: Add notebook for Direct Adjustments

[dgbarclay]

Pull Request Checklist

• [x] Changes follow the style guide
• [x] Tests pass
• [x] Raised the PR against the develop branch

Description of the PR

This notebook demonstrates how to create transactions that update the units of an holding without having any impact on the cost.

[review-notebook-app[bot]]

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[adamMQM]

/LGTM