Anonymized real world data set

The test data is great, but makes it hard to test performance at the scale Suggestomatic was intended for. Internally at Causes we have a test set of about 900m records, we should obfuscate group and user ids and release the large scale data set.

Start by reviewing the repository's existing test data and performance-testing setup. Determine how the roughly 900 million records could be obfuscated and released, with group and user identities protected. Done means an anonymized large-scale dataset is available for performance testing.

Written by the indexing model from the issue text.