Migrate the CMS Production Workload Management system from CouchDB 1.6.x to CouchDB 3.1.x

The CMS Production Workload Management system drives all the Monte Carlo and data processing activities in the Experiment: through it millions of jobs are submitted to the World Wide Computing Grid every month, making it a crucial component in the CMS Computing Infrastructure. Another crucial technology in this ecosystem is the NoSQL database Apache CouchDB, which is largely used in the Workload Management System. This report summarizes the summer student work of the adoption of the latest CouchDB version 3.1.x in CMS Computing, ensuring that database replications and new features are explored at their best, as well as benchmarking and applying any possible optimizations to the system. At the end, a brief outlook on unfinished milestones and a potential CouchDB 4 migration is given.