[Fleet] Migrate Fleet's saved objects from namespaceType: agnostic to namespaceType: single

[kpollich]

Ref #180708

Today, Fleet's saved objects are defined with namespaceType: "agnostic", meaning each object is considered "global" and has no affinity for Kibana spaces. This is problematic for users who rely on Kibana spaces for access control, and makes Fleet difficult to use in managed service provider use cases.

kibana/x-pack/plugins/fleet/server/saved_objects/index.ts

Lines 123 to 132 in f1e02f6

	[AGENT_POLICY_SAVED_OBJECT_TYPE]: {
	name: AGENT_POLICY_SAVED_OBJECT_TYPE,
	indexPattern: INGEST_SAVED_OBJECT_INDEX,
	hidden: false,
	namespaceType: 'agnostic',
	management: {
	importableAndExportable: false,
	},
	mappings: {
	properties: {

As part of the large effort to move Fleet and Integrations towards full support for Kibana spaces, we need to migrate all of Fleet's saved object definitions to a new space aware namespaceType designation. See these Kibana docs for more context on how different namespaceType settings behave.

To simplify this migration, Fleet's saved objects should be changed from their current agnostic definition to single. We won't be supporting any use cases where Fleet objects can exist in multiple spaces, and moving to single for existing objects saved us a lot of work in Kibana's core APIs to support the migration.

Implementation checklist

• Create a feature flag to gate space awareness as a whole
• Update Fleet's saved object definitions to set namespaceType to single if the feature flag is enabled
• Fleet's various "settings" types should remain global, e.g. fleet server hosts, proxies, outputs, and agent binary download sources

[elasticmachine]

Pinging @elastic/fleet (Team:Fleet)

[nchaulet]

The exact naming/versioning scheme for these new SO types is TBD

It could be a good opportunity to get ride of the ingest prefix and rename these SO fleet-*

[kpollich]

I've updated this issue to capture the new designation of single instead of multiple-isolated.

[cmacknz]

Update Fleet's saved object definitions to set namespaceType to single if the feature flag is enabled

If the feature flag is enabled and then disabled, is this process reversed? Or is this a one shot conversion with no way back?

[kpollich]

If the feature flag is enabled and then disabled, is this process reversed? Or is this a one shot conversion with no way back?

I just tested toggling the feature flag back and forth and Kibana allows toggling between global objects + single-space objects back and forth. Objects before/after the toggle behave as expected.