Create an informative issue (See each section, incomplete templates/issues won't be triaged)

Using the current documentation as a model, please complete the issue template. 

Note: Doc team updates the current version and the two previous versions (n-2). For earlier versions, we will address only high-priority, customer-reported issues for releases in support.

Prerequisite: Start with what we have

Always look at the current documentation to describe the change that is needed. Use the source or portal link for Step 3:

 - Use the Customer Portal: https://access.redhat.com/documentation/en-us/red_hat_advanced_cluster_management_for_kubernetes/2.6

 - Use the GitHub link to find the staged docs in the repository: https://github.com/stolostron/rhacm-docs 

Describe the changes in the doc and link to your dev story

Provide info for the following steps:

1. - [ ] Mandatory Choose the documentation release (Published releases are refreshed ~weekly after publication). 
     
      - [ ] ACM 2.4
      - [ ] ACM 2.5
      - [x]ACM 2.8 (upcoming release)

      - [ ] MCE 2.0
      - [ ] MCE 2.1 
      - [x MCE 2.3 (upcoming release)
   

2. - [ ] Mandatory Choose the type of documentation change.

      - [ ] New topic in an existing section or new section
      - [x] Update to an existing topic

3. - [ ] Mandatory for bugs: What is the diff? Clearly define what the problem is, what the change is, and link to the current documentation:

Current: https://access.redhat.com/documentation/en-us/red_hat_advanced_cluster_management_for_kubernetes/2.7/html/clusters/cluster_mce_overview#creating-a-credential-for-openstack

what was previously a manual method to use your own Internal CA to provision a cluster on OpenStack was described here:
https://access.redhat.com/articles/6495941

this is now supported in the UI

1. when using the Crendtial Wizard to create a credential for OpenStack, in the second step, there is now a field for the user to enter that Internal CA

2. If the the user enters that optional CA, the Credential wizard automagically adds the "cacert: /etc/openstack-ca/ca.crt" to the cluster.yaml field above it

3. Now when the user goes to create the cluster with that credential, this CA and the reference to it are automagically added to the cluster yaml