Duplicate name error in index template creation is signaled only at the end of the wizard

[monfera]

Kibana version: 7.14

Elasticsearch version:

Server OS version:

Browser version:

Browser OS version:

Original install method (e.g. download page, yum, from source, etc.):

Describe the bug:

Steps to reproduce:

1. Create an index template with a duplicate name
2. Go through the pages
3. You only get an error once you want to save it

Expected behavior: It should be like when an index pattern is missing: it should stop the user right then and there on the suboptimally named "Logistics" page

Screenshots (if relevant):

Errors in browser console (if relevant):

Provide logs and/or server output (if relevant):

Any additional context:

cc @yuliacech

[elasticmachine]

Pinging @elastic/kibana-stack-management (Team:Stack Management)

[monfera]

There is a likely related issue: changing the name from a duplicate name to a legit name doesn't remove the error, and it doesn't even yield the same treatment that adding the original bad name yielded (which did NOT show an error until trying to save it):

https://user-images.githubusercontent.com/1548516/125839810-e6c984ff-357b-46db-869f-ccfa32c2ffa2.mp4

Of course, there's some chance that some other user, or the user herself/himself creates an identically named index template in another browser tab. So the validation at the end is needed. But it's still better UX to validate early, at the location and time of specifying the name

[fdartayre]

To be noted, it is possible to create index patterns with the same name:

• with the REST API (https://github.com/elastic/kibana/issues/107359)
• Exporting the index pattern as a saved object and re-importing choosing "Create new objects with random IDs"

This doesn't appear to be very consistent.

[elasticmachine]

Pinging @elastic/kibana-management (Team:Kibana Management)