Allow external AlertManagers to be visible in the list of AlertManagers on the built-in Prometheus

1. Who is the customer behind the request?
Account: 788243
TAM customer: Bell Mobility
CSM customer: Bell Mobility
Strategic: OpenShift 4.x Monitoring Imporvement

2. What is the nature and description of the request?
External ALertManager is not visible within the local and built-in Prometheus.

3. Why does the customer need this? (List the business requirements here)
We have an external central point to monitor all our environment and we need to avoid deduplication of Alert routing configuration and keep our Monitoring flow simpler.

4. How would the customer like to achieve this? (List the functional requirements here)

• Allow built-in Prometheus to send alerts to an external AlertManager

5. For each functional requirement listed, specify how Red Hat and the customer can test to confirm the requirement is successfully implemented.

• We can work with someone from the RedHat OpenShift Monitoring team to find a way to allow our external AlaertManager to receive alerts coming from the built-in Prometheus.
  We have the environment in place and a SandBox that can be leveraged for this purpose

6. Does the customer have any specific timeline dependencies and which release would they like to target (i.e. RHEL5, RHEL6)?
We are running OCP4.6 15 and we aim to have someone working with us within the three weeks of March 1st till March 19th if possible

7. Is the sales team involved in this request and do they have any additional input?
We are part of Bell that having a huge service with RedHat and we paid for our support of 30 computes for OCP4 as Premium

8. List any affected packages or components.
OCP Prometheus Monitoring and Aerting

9. Would the customer be able to assist in testing this functionality if implemented?
We agree on this as per the proposal in the question #6