Sample App: Notification Service: camel slack sink

[Leo6Leo]

Problem

Create the necessary yaml files to configure the camel slack sink and triggers.

More implementation details can be found in the design doc here.

Persona:

Which persona is this feature for?
Administrators and developers

Exit Criteria

• yaml files to configure the camel slack sink
• Should test the yaml file locally and make sure the message delivery works before the PR get merged.
• A documentation that clearly explains the steps on how to set up the slack sink and how it works.

Time Estimate (optional):
How many developer-days do you think this may take to resolve?
1-2

Additional context (optional)

The notification message will be sent to a slack sink by using camel knative slack sink.