* add minimal working is_null filter
* add is_null condition to grpc api (backward compatible)
* add unit tests is_null and is_empty conditions
* add is_null to points.proto file
* add some failing OpenAPI tests
* fix a failing test due to change in collection data
* refactor MultiValue's check for is_null
* fix is_empty condition not picking up "key":[]
* remove duplicate OpenAPI integration test
* reuse same variable in condition checker tests
* update grpc docs
* fix is_null cardinality estimation to match is_empty
* update openapi specs
* remove unused debug statements
* add new test points to original test_collection
* fix failing tests according to newly added points
* add the `"key":[null]` test_case
* wip: re-implement http tests using openapi validation library
* collection delete api
* payload operations test
* payload delete operations test
* payload index creation and removing test
* uuid operations test
* schema consistency test
* add tests into pipeline
* chmod +x
* faster local runs with docker cache
* upd instruction
