Release v0.8.0

What's Changed

• Make choice of aggregator dynamic at session level and additional aggregators (FedOpt) by @ahellander in #498
• Fixes the issue with number of files/storage growing on combiner by @ahellander in #503
• Use latest mongodb and bump version number by @ahellander in #502
• Feature/cross device simulation by @ahellander in #504
• Add docker compose override file for async example by @ahellander in #505
• Docs/SK-646 | Add aggregators and helpers by @Wrede in #508
• Feature/SK-634 | Add logging to controller by @ahellander in #506
• Feature/SK-622 | Session object should store committed_at in date format by @niklastheman in #510
• Feature/retire dashboard by @ahellander in #509
• Feature/SK-660 | Clean up numpyhelper from unused methods by @Wrede in #512
• Docs update to reflect recent refactoring by @ahellander in #511
• Link to docs tutorial from main readme by @ahellander in #519
• Updated FAQ docs by @ahellander in #518
• Feature/SK-658 | Add gRPC healthchecking by @ahellander in #515
• Bugfix/SK-673 | start_session endpoint should have delete_models=True by @Wrede in #521
• Feature/SK-667 | Add new Android helper to Fedn by @niklastheman in #524
• Bug/SK-680 | Android helper imports helper base incorrectly by @niklastheman in #525
• Feature/SK-676 | If no compute package is set when starting a session, Fedn should say so by @niklastheman in #522
• Feature/SK-623 | Validations objects should store proper timestamp by @niklastheman in #526
• Feature/SK-684 | Events should store proper timestamps by @niklastheman in #527
• Bugfix/SK-675 | Model staging not in sync, TaskStream by @Wrede in #523

Full Changelog: v0.7.1...v0.8.0