[OAS] Migrate remaining ASCII docs to OAS

[jloleysens]

The following APIs should migrate to documenting their APIs in code so that OAS can be generated or them and hosted on our new API reference site.

See this script for paths that are currently extracted from code and included in the OAS bundle for hosting.

APIs to migrate are:

• Features @elastic/kibana-core
• Privileges @elastic/kibana-security
• User sessions @elastic/kibana-security
• Logstash @elastic/logstash
• Short URLs @elastic/appex-sharedux
• Task manager health @elastic/response-ops
• Upgrade Assistant @elastic/kibana-core OR @elastic/kibana-management
• Synthetics @elastic/obs-ux-management-team
• Uptime @elastic/obs-ux-management-team

Please update this issue once they are included in the generated OAS bundle by:

1. Adding metadata to your router registered route
2. Updating the script to include your API when capturing a snapshot

See the following comprehensive examples 1, 2 or search for meta: inside any **/routes/* files in the code base.

See the docs