Add top level boolean logic operator for signals

[VaibhavPage]

Is your feature request related to a problem? Please describe.
With current Sensor spec, user can only use AND operator for multiple signals and it lacks support for complex signals circuiting.

Describe the solution you'd like
Use "--" for OR operator and "-" for AND operator.

Example-

signals:
   -- name: time
      calender:
        interval: 10s
    - name: minioS3
      artifact:
        s3:
          bucket: hello
          endpoint: artifacts-minio.default:9000
          insecure: true
          accessKey:
            key: accesskey
            name: artifacts-minio
          secretKey:
            key: secretkey
            name: artifacts-minio
          event: s3:ObjectCreated:Put
          arn:
            partition: minio
            service: sqs
            region: us-east-1
            accountID: "1"
            resource: nats
        stream:
          nats:
            url: nats://example-nats-cluster:4222
            subject: bucketevents
   -- name: worklow-1
       resource:
         namespace: default
         group: "argoproj.io"
         version: "v1alpha1"
         kind: "Workflow"
         filter:
           prefix: scripts-bash
           labels:
             workflows.argoproj.io/phase: Succeeded 
      

[magaldima]

I have thought about this in terms of implementing the basic buildings blocks of binary logic as in circuit AND and OR logic gates. This does make sense to me and would be a valuable feature for signals, however I think there has to be a more evident and transparent way to define AND/OR logic in the signal specification than using - vs --.

[VaibhavPage]

I feel this feature is essential to make framework easy to use. Basically, without support for OR operator, you end up writing multiple sensors that trigger same workflow. e.g. consider your gateway is generating 4 different configuration, and for each event we want to create same workflow, then adding these 4 signals in one sensor will cause sensor to wait on all 4 signals, definitely what we wanted.

[VaibhavPage]

https://github.com/Knetic/govaluate does the job