[SIEM][Detection Engine] REST API improvements and changes from UI/UX feedback

[FrankHassanabad]

Summary

Updated REST API from feedback from the UI/UX

• Changes the id to be rule_id on PUT/POST and makes it optional for a POST (create).
• On data return sets both id and rule_id is returned. If rule_id is not set, a uuid.v4() will b assigned to the rule_id and the value will be returned.
• Transforms output of all endpoints to be 1-1 to the input.
• Fixes delete to return the deleted rule
• Changes the URL to be /api/detection_engine/rules
• Changes the POST behavior to fail with a 409 (conflict) if the rule already exists (For creates)
• Changes the POST behavior where sending in a rule_id is now optional. If none are sent in it does not create a rule_id and instead returns null for the rule_id and the autogenerated one.
• Changes the PUT behavior to fail with a 404 (not found) if the rule does not already exist (For updates)
• Deletes the actions code and just uses an empty array since we don't have actions yet
• Makes all error conditions consistent and does not expose the underlying error codes. Only exception to the rule is if an error condition returns non 404 or something unexpected. In which case it will show that error upstream.

Example post output:

$ ./post_signal.sh
{
  "created_by": "elastic",
  "description": "Detecting root and admin users",
  "enabled": true,
  "false_positives": [],
  "from": "now-6m",
  "id": "8277a0e8-474c-4507-9c11-5f197b5fe2d5",
  "index": [
    "auditbeat-*",
    "filebeat-*",
    "packetbeat-*",
    "winlogbeat-*"
  ],
  "interval": "5m",
  "rule_id": "rule-1",
  "language": "kuery",
  "max_signals": 100,
  "name": "Detect Root/Admin Users",
  "query": "user.name: root or user.name: admin",
  "references": [
    "http://www.example.com",
    "https://ww.example.com"
  ],
  "severity": "high",
  "updated_by": "elastic",
  "tags": [],
  "to": "now",
  "type": "query"
}

Example delete and get URL's now (see scripts for more details):

${KIBANA_URL}/api/detection_engine/rules?rule_id="rule-1"
${KIBANA_URL}/api/detection_engine/rules?id="04128c15-0d1b-4716-a4c5-46997ac7f3bd"

Checklist

Use strikethroughs to remove checklist items you don't feel are applicable to this PR.

- [ ] This was checked for cross-browser compatibility, including a check against IE11

- [ ] Any text added follows EUI's writing guidelines, uses sentence case text and includes i18n support

- [ ] Documentation was added for features that require explanation or tutorials

• Unit or functional tests were updated or added to match the most common scenarios

- [ ] This was checked for keyboard-only and screenreader accessibility

For maintainers

- [ ] This was checked for breaking API changes and was labeled appropriately

• This includes a feature addition or change that requires a release note and was labeled appropriately

[elasticmachine]

Pinging @elastic/siem (Team:SIEM)

[spong]

Tested scripts locally and observed the new rule interface and rule_id/id changes across the API. Also 👀through the code changes and all the new tests -- great job with this @FrankHassanabad, the API and flow is really coming together! And thanks for all these sweet new additions, going to make use of them in the UI right away! 🙂

[elasticmachine]

💚 Build Succeeded

• continuous-integration/kibana-ci/pull-request
• Commit: f9b17d8

[elasticmachine]

💚 Build Succeeded

• continuous-integration/kibana-ci/pull-request
• Commit: 520a6dd