[Uptime] [UI Monitor Management] Hide all corresponding pages and new features behind a feature flag

[dominiqueclarke]

UI Monitor Management should only be available behind an explicit feature flag.

The feature flag will be xpack.uptime.ui.unsafe.monitorManagement.enabled.

Corresponding UI Monitor management routes should be unavailable when xpack.uptime.ui.unsafe.monitorManagement.enabled is false and available when xpack.uptime.ui.unsafe.monitorManagement.enabled is true.

To enable/disable server part of monitor management, see #421

[lucasfcosta]

⚠️ Please notice that this feature flag did not show me the links to the UI monitor management screens on version 8.0, I had to test it on 8.1, and thus I believe it needs fixing.
I tested this on the current tip of the 8.0 branch, whose hash is 11772615c663fafca30540801c0aba3ae4d462e6.

I've just had to test this on 8.1 by following the steps below:

1. Enabling the UI Monitor Management flag in kibana.yml:

   # kibana.dev.yml
   xpack.uptime.ui.unsafe.monitorManagement.enabled: true

2. After enabling that, I do see the "monitor management" link on the top right corner of the Uptime app, as shown in the screenshot below.
   

3. In that page, I can also access the add-monitor page by clicking the "Add monitor" button on the top right corner of the page, as shown in the screenshot below. Furthermore, editing and deleting the monitor is not a problem.
   
   
   

4. Finally, when I disable the UI Monitor Management flag in kibana.yml, I can't see those pages anymore.

   # kibana.dev.yml
   xpack.uptime.ui.unsafe.monitorManagement.enabled: false

   When I try to access these pages directly through the routes, I also get a 404.

   

   

   On another note, should we open a separate issue for the design of these 404 pages?

Worth highlighting again: it works on 8.1, but not on 8.0.

I also tested only the CRUD functionality, not running these with the service itself, which I plan on doing separately.

[dominiqueclarke]

To clarify, the service is not expected to work in 8.0. We were working on individual features before the 8.0 FF, but post FF we added more MVP features. As such, the work to test that the FF works positively can be done in 8.1.0.

[lucasfcosta]

As per the comment above by @dominiqueclarke and what we discussed on Slack, I'll move on to moving this issue to "Done done" as the testing has been done in 8.1.0 successfully.