how to group by string pattern (not necessarily regex) in mongoDB aggregation

Question

I have a dataset in the collection with following schema:

[
    {"status": "Completed", "datetime_field": "2021-01-01T00:00:00.000Z", "aother_field_key": "aother_field_values"},
    {"status": "Completed", "datetime_field": "2021-01-02T00:00:00.000Z", "aother_field_key": "aother_field_values"},
    {"status": "New", "datetime_field": "2021-01-02T00:00:00.000Z", "aother_field_key": "aother_field_values"},
    {"status": "Cancelled - type 0", "datetime_field": "2021-01-01T00:00:00.000Z", "aother_field_key": "aother_field_values"},
    {"status": "Draft", "datetime_field": "2021-01-03T00:00:00.000Z", "aother_field_key": "aother_field_values"},
    {"status": "Completed", "datetime_field": "2021-01-01T00:00:00.000Z", "aother_field_key": "aother_field_values"},
    {"status": "Cancelled - type 1", "datetime_field": "2021-01-04T00:00:00.000Z", "aother_field_key": "aother_field_values"},
    {"status": "Cancelled - type 2", "datetime_field": "2021-01-01T00:00:00.000Z", "aother_field_key": "aother_field_values"},
    {"status": "Deleted", "datetime_field": "2021-01-05T00:00:00.000Z", "aother_field_key": "aother_field_values"},
    {"status": "Completed", "datetime_field": "2021-01-01T00:00:00.000Z", "aother_field_key": "aother_field_values"},
    {"status": "Completed", "datetime_field": "2021-01-01T00:00:00.000Z", "aother_field_key": "aother_field_values"}
]

And I want to group by both datetime_field and status fields in mongoDB aggregation pipeline. I know that for the datetime field using $dateToString operator can easily control the granularity of grouping by datetime. The issue I'm having is to group by the status.

As you can see there are more than one type of Cancelled status, if simply do {$group: {_id: {status: '$status'}}} it will separate the different types of Cancelled, is there a way to group all different types of Cancelled into one group?

Thanks!

Answer 1

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