[FEATURE REQUEST] aggregation task optimization

[shuqingzai]

Is your feature request related to a problem? Please describe.
Several problems were discovered using task aggregation:

1. There is no error returned in the task aggregation interface. An error return should be added. When a large number of tasks are aggregated, errors will inevitably occur. If the error is returned, this aggregation task should be ignored.

See:

• asynq/aggregator.go

  Line 161 in d04888e

  aggregatedTask := a.ga.Aggregate(gname, tasks)

• asynq/server.go

  Line 263 in d04888e

  Aggregate(group string, tasks []*Task) *Task

2. When using the aggregation task function, you cannot set additional options, such as: task delay

See:

asynq/aggregator.go

Line 163 in d04888e

if _, err := a.client.EnqueueContext(ctx, aggregatedTask, Queue(qname)); err != nil {

3. Aggregation capabilities at the queue task level cannot be set, and aggregation can only be set at the server level, which is not very suitable for some complex aggregation requirements.

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