Setup Slack as an event source

[shubhamgandhi1996]

wanted to know what does the token and signing secrete means in the slack event source example and how to create that?

`apiVersion: argoproj.io/v1alpha1
kind: EventSource
metadata:
name: slack
spec:
service:
ports:
- port: 12000
targetPort: 12000
slack:
example-insecure:
# hook contains configuration for the HTTP server running in the event-source.
# Slack will send events to following port and endpoint
webhook:
# endpoint to listen events on
endpoint: "/"
# port to run HTTP server on
port: "12000"
# HTTP request method to allow. In this case, only POST requests are accepted
method: POST
# token contains information about K8s secret that stores the token
token:
# Name of the K8s secret that contains the token
name: slack-secret
# Key within the K8s secret whose corresponding value (must be base64 encoded) is token
key: tokenkey
# signingSecret contains information about the K8s secret that stores
# Slack Signing Secret used to sign every request from Slack
signingSecret:
# Name of the K8s secret that contains the signingSecret
name: slack-secret
# Key within the K8s secret whose corresponding value contains the
# base64-encoded Slack signing secret
key: signingSecret

# with secure connection
example-secure:
  webhook:
    endpoint: "/"
    port: "14000"
    method: "POST"
    # k8s secret that contains the cert
    serverCertSecret:
      name: my-secret
      key: cert-key
    # k8s secret that contains the private key
    serverKeySecret:
      name: my-secret
      key: pk-key
  token:
    name: slack-secret
    key: tokenkey
  signingSecret:
    # Name of the K8s secret that contains the signingSecret
    name: slack-secret
    # Key within the K8s secret whose corresponding value contains the
    # base64-encoded Slack signing secret
    key: signingSecret`