Silent incident

[b0n54i]

Description

This PR adds the option to create private incidents at time of opening an incident using the /hellper_incident command.

How to test?

• Create an silent incident

Feature: /hellper_incident
Given I'm creating an incident 
When I select the 'yes' option in the "This is a silent incident?" field
Then the incident must be created without the  HELLPER_PRODUCT_CHANNEL_ID being notified and the incident channel must be private

• Resolve an silent incident

Feature: /hellper_resolve
Given a silent incident was created
When I resolve this incident
Then the incident must be resolved without the  HELLPER_PRODUCT_CHANNEL_ID being notified

• Close an silent incident

Feature: /hellper_close
Given a silent incident was created
When I close this incident
Then the incident must be closed without the  HELLPER_PRODUCT_CHANNEL_ID being notified

• Cancel an silent incident

Feature: /hellper_cancel
Given a silent incident was created
When I cancel this incident
Then the incident must be canceled without the  HELLPER_PRODUCT_CHANNEL_ID being notified

• List Active Incidents

Feature: cmd/notify
Given a silent incident was created
When the cron job (./notify) lists active incidents
Then the incident should not appear in this list

[GLOFonseca]

Left some comments

[GLOFonseca]

Code approved.

Testing on the staging environment is important!