Delete participations of long inactive users #3647

Job	Run time
Compile Scss	1m 15s
Backup process	3m 1s
Formatting	1m 15s
Linter	1m 50s
Build nix environment on MacOS	3m 41s
MyPy	1m 20s
Render Html pages	1m 30s
Test + Coverage	2m 15s
Test (shuffled order)	1m 53s
Test Typescript	2m 5s
	20m 5s

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