[SIEM][Detection Engine] Setup possible with read-only space privilege

[cwurm]

Scenario:
Trying to set up the DE with reduced privileges.

Privileges:

• Cluster: manage_ilm, manage_index_templates
• Index: all on *
• Kibana: Read on SIEM

What did I do? Navigate to Detections tab

Behavior: Sets up the DE signals index even though the user has read-only space privileges.

Suggestion:
Do not try to set up signals index with only a Read space privilege.

[elasticmachine]

Pinging @elastic/siem (Team:SIEM)