[Meta] Kibana 8.0 breaking changes

[kobelb]

We've been asking people to create issues using the 8.0 Breaking change issue template for all breaking changes that they'd like to see accommodated for in the 8.0 Upgrade Assistant. The following attempts to categorize them based on their subject-matter:

kibana.yml setting

Removed

Issue	# of users impacted
Remove kibana.defaultAppId #54088	Low
Remove map.regionmap.* kibana.yml settings #81704	?
Remove proxyElasticMapsServiceInMaps yml setting #82132	Low
Prevent disabling the spaces plugin #82467	Low
Logging configuration format change #84363	High

Renamed

Issue	# of users impacted
New format for the authentication config #82113	High
Move xpack.telemetry.* config to telemetry.* #82432	Low

Miscellaneous

Issue	# of users impacted
Forbid using elasticsearch.ssl.certificate without elasticsearch.ssl.key and vice versa #81746	?
Provide sensible defaults for xpack.security.session.{lifespan|idleTimeout} #81747	Low

Saved-object

Issue	# of users impacted
Remove expression-based scripted fields from Kibana. #77669	Low
Remove Coordinate map and region map visualizations #81703	High

Security

Role

Issue	# of users impacted
kibana_user role removed and replaced by kibana_admin #81674	High
Dashboard only mode has been removed #81690	Low
reporting_user role is removed #92485	Medium

User

Issue	# of users impacted
kibana user removed and replaced by kibana_system #81680	High

HTTP API

Issue	# of users impacted
Drop /api/security/v1/saml route in favour of /api/security/saml/callback #81733	High
Drop support for copy/import conflicts ("pseudo copies") #81904	?

Kibana UI Feature

Issue	# of users impacted
Drop support for copy/import conflicts ("pseudo copies") #81904	?
Removal of Timelion app #82702	Low

Logging output

Issue	# of users impacted
Audit logging events have changed #82578	Medium
Logging configuration format change #84363	High

Miscellaneous

Issue	# of users impacted
[APM] 8.0 breaking changes #83256	?

[Bamieh]

Adding this to the list:

Drop suppport for server.host: "0" in kibana config:

Consider dropping support for '0' in v8.0.0. This value is passed
to hapi, which validates it. Prior to hapi v20, '0' was considered a
valid host, however the validation logic internally in hapi was
re-written for v20 and hapi no longer considers '0' a valid host. For
details, see: #86716 (comment)

Context: #86806

[watson]

@Bamieh I've created #87114 to get this fixed in master

[kobelb]

I'm closing this issue, as it's fallen out of date as people have been able to integrate directly with the upgrade assistant.