Kibana's Docker Image is slow to access the `Case` UI of `Security` when the `XPACK_ENCRYPTEDSAVEDOBJECTS_ENCRYPTIONKEY` environment variable is not set

[linghengqian]

• I came from https://discuss.elastic.co/t/why-is-kibanas-docker-image-slow-to-access-the-security-s-case-ui-when-the-xpack-encryptedsavedobjects-encryptionkey-environment-variable-is-not-set/366093?u=linghengqian , in order to avoid the original discussion being closed due to no reply for 28 days, I opened the current github issue.
• Assume that there is a Docker Compose file es01-docker.yaml as follows,

  name: test
  services:
  es01:
  image: docker.elastic.co/elasticsearch/elasticsearch:8.15.0
  environment:
    - ELASTIC_PASSWORD=es01Test
    - "discovery.type=single-node"
    - "xpack.security.http.ssl.enabled=false"
  networks:
    - elastic-net
  ports:
    - "9200:9200"
  networks:
  elastic-net:

• Assume that there is a Docker Compose file kibana-docker.yaml as follows,

  name: test
  services:
  kibana:
  image: docker.elastic.co/kibana/kibana:8.15.0
  environment:
    - ELASTICSEARCH_URL=http://es01:9200
    - ELASTICSEARCH_HOSTS=http://es01:9200
    - ELASTICSEARCH_USERNAME=kibana_system
    - ELASTICSEARCH_PASSWORD=kibanaTest
    - XPACK_SECURITY_ENABLED=false
  ports:
    - "5601:5601"
  networks:
    - test_elastic-net
  networks:
  test_elastic-net:
  external: true

• Start Elasticsearch and Kibana using the following bash command:

  docker compose --file ./es01-docker.yaml up -d
  curl -u elastic:es01Test \
  -X POST \
  http://127.0.0.1:9200/_security/user/kibana_system/_password \
  -d '{"password":"'"kibanaTest"'"}' \
  -H 'Content-Type: application/json'
  docker compose --file ./kibana-docker.yml up -d

• Then visit http://localhost:5601 and enter the account elastic and password es01Test. Enter the Case interface of Security.
• 
• This will lead to a long wait. Maybe 3 seconds.
• 
• After a while, a large number of Error Logs will load the screen, and new Error Logs will be continuously loaded. Kibana will only remind you to set XPACK_ENCRYPTEDSAVEDOBJECTS_ENCRYPTIONKEY.
• 
• If I set the XPACK_ENCRYPTEDSAVEDOBJECTS_ENCRYPTIONKEY environment variable for Kibana's Docker Container, none of this happens. If the corresponding environment variables are set, this interface loads very quickly.
• Why is Kibana's Docker Image slow to access the Security's Case UI when the XPACK_ENCRYPTEDSAVEDOBJECTS_ENCRYPTIONKEY environment variable is not set?
• If this webpage requires the existence of the environment variable XPACK_ENCRYPTEDSAVEDOBJECTS_ENCRYPTIONKEY to be used, it is unreasonable from my point of view. It would be more reasonable not to display the entry of this webpage in Kibana when the environment variable XPACK_ENCRYPTEDSAVEDOBJECTS_ENCRYPTIONKEY does not exist.

[elasticmachine]

Pinging @elastic/kibana-operations (Team:Operations)

[elasticmachine]

Pinging @elastic/response-ops-cases (Feature:Cases)