Fix(grouper): grouping patterns

[e11sy]

Problem

• grouping patterns are stored in db in format

export interface ProjectEventGroupingPatternsDBScheme {
    /**
     * If of the pattern
     */
    _id: ObjectId;
    /**
     * String that represents regular expression pattern
     */
    pattern: string;
}

but we are treating them as string[]. That leads to this type of errors:

2025-07-17T14:33:40.699Z error: Error while getting original event for pattern [object Object] 

• also this issue is invisible for tests because of incorrect grouping patterns mocking (they are mocked as string[] as well)

Solution

• Treat grouping patterns as described in ProjectEventGroupingPatternsDBScheme interface (as they actually stored)
• Fix mocks in tests