Exclude unenrolled clients from analysis

[scholtzan]

Currently, all clients that enrolled during the enrollment period will be part of all analysis runs, even if the clients have unenrolled. Ideally, we want to exclude unenrolled clients. Excluding clients after the enrollment period has ended might have an impact on the analysis results, so as a first step we should exclude clients that unenrolled while the enrollment period was still active.

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