Remove Transport Layer Security (TLS) requirement for alerting when security is enabled

[mikecote]

Once elastic/elasticsearch#76801 merges, Elasticsearch no longer requires TLS to be enabled to use API keys. As a follow-up, we can remove the enforcement checks the alerting framework does and enable usage when TLS is disabled, and security is enabled.

cc @arisonl

[elasticmachine]

Pinging @elastic/kibana-alerting-services (Team:Alerting Services)

[mikecote]

Adding blocked label until elastic/elasticsearch#76801 is merged.

[mikecote]

Since we are using security?.authc.apiKeys.areAPIKeysEnabled(), we may get this fix for free 🤔 might be worth validating. We still need to disable the usage of alerting if ever a customer sets xpack.security.authc.api_key.enabled: false in Elasticsearch.

[mikecote]

elastic/elasticsearch#76801 is now merged and backported, removing blocked label.

[mikecote]

Expanding on #111721 (comment).

The security?.authc.apiKeys.areAPIKeysEnabled() makes it seem that alerting will work without TLS. If that is the case, without changing our code, users can encounter 2 scenarios that would be misleading.

Scenario 1: User reads docs, spends time to set up TLS when alerting works without TLS enabled (wasting set-up steps)
Scenario 2: User disables API keys and gets a banner asking for TLS to be enabled (when it fact it doesn’t need to be)