The `sum()` and `count()` functions were giving results different from the openCypher specification on null `input.` The aggregation functions also had a problem when they were used in a group-by context and were giving results that were not compliant with the openCypher specification.
* Modify `toString` to be able to handle `Date`, `LocalTime`, `LocalDateTime` and `Duration`
* Add unit tests
* Make `operator<<` use the `ToString()` implementations
* Add tests to verify the correctness of negative durations
* Add more tests to look for cases when the individual duration entities overflow.
* Storage takes care of the saving of setting when a new replica is added
* Restore replicas at startup
* Modify interactive_mg_runner + memgraph to support that data-directory can be configured in CONTEXT
* Extend e2e test
* Correct typo
* Add flag to config to specify when replication should be stored (true by default when starting Memgraph)
* Remove un-necessary "--" in yaml file
* Make sure Memgraph stops if a replica can't be restored.
* Add UT covering the parsing of ReplicaStatus to/from json
* Add assert in e2e script to check that a port is free before using it
* Add test covering crash on Jepsen
* Make sure applciaiton crashes if it starts on corrupted replications' info
Starting with a non-reponsive replica is allowed.
* Add temporary startup flag: this is needed so jepsen do not automatically restore replica on startup of main. This will be removed in T0835
* Extend mgp_module with include adding functions
* Add return type to the function API
* Change Cypher grammar
* Add Python support for functions
* Implement error handling
* E2e tests for functions
* Write cpp e2e functions
* Create mg.functions() procedure
* Implement case insensitivity for user-defined Magic Functions.
