[Uptime] Add settings page

[andrewvc]

Per elastic/uptime#43 we should add a settings page to uptime to allow per-space dynamic settings. This is the implementation issue for elastic/uptime#43.

Fixed in #53550

[elasticmachine]

Pinging @elastic/uptime (Team:uptime)

[justinkambic]

Test plan overview

I'm reviewing this issue as part of our test plan. Here are the steps I plan to follow:

Test scenario

I have two heartbeat instances. One writes to an index named heartbeat-public, the other writes to an index named heartbeat-secret.

Configure multiple spaces and index patterns

I (an admin) am going to create two different spaces, one for a user named Jen and another for a user named Jordan. Jen needs to see the status of all our org's public sites, along with hidden endpoints. People in Jordan's role only know/care about the public sites.

Using the settings page, I will configure Jen's space to find an index pattern like heartbeat-*, and Jordan's space will use a pattern like heartbeat-public*. This way, Jen can see all the endpoints we monitor, while Jordan will only see the public ones.

Modifying index patterns

Later, we decide to re-alias the name of the public index to heartbeat-unrestricted. I (the admin) will modify the dynamic setting for the index pattern in Jordan's space to be heartbeat-unrestricted*. No need to modify Jen's space settings.

Preventing unwanted modification

Jordan decides he thinks the index pattern name should be something different. He logs into his Kibana and attempts to modify the dynamic setting for the space's index pattern. Fortunately for the rest of his team (using the same space), he is a readonly user and cannot do this.

Meanwhile, Jen's space hasn't changed and she is happily monitoring the entire environment, which never experiences any downtime.

[justinkambic]

Test renumeration

0. pull 7.7 branch
1. Started fresh snapshot with yarn es snapshot
2. Start up kibana
3. Configure beat 1 to write to heartbeat-secret-{version}-{date}
4. Run beat 1
5. Configure beat 2 to write to heartbeat-public-{version}-{date}
6. Login to Kibana as super user
7. Create Jen's space
   
8. Create Jordan's space
   
9. Define a role for Jordan and Jen. Even though they're accessing different spaces, neither should be able to modify the settings in their space, so their permission levels will be the same.
   
10. Create Jordan and Jen users
    
11. As admin, set the dynamic index patterns for each space
    
    
12. Log in as Jen, she can see both locations (i.e. data from each HB instance we're running)
    
13. Log in as Jordan, he can only see the data from one location, the heartbeat-public* index
    
14. As admin, create an alias for the public index pattern
    
15. As admin, redefine the dynamic index pattern in Jordan's space
    
16. Jordan's page still loads data with the new index pattern (note, I had to provide Jordan's role with the manage permission
17. Jordan, a readonly user, attempts to change the index pattern for his space but cannot