Remove support for legacy imports from the UI

[joshdover]

Related to #41439

In Kibana 8.0, we will no longer support the legacy export format from Kibana 6.x. We've had a warning in place in the UI since 7.0 that these exports will no longer be supported.

This is issue is to scope out removal of the UI code for handling legacy imports. This code leverages the SavedObjectLoader pattern for saving these objects to the backend. These loaders can now be removed once we stop supporting legacy exports (#67607).

This should probably happen in a multiple phases:

• Remove support from the top-most UI layer for legacy imports
  • The UI should simply not allow .json files to be selected by the file picker and should remove all code that hooks into the legacy imports:
    • Remove legacyImport:

      kibana/src/plugins/saved_objects_management/public/management_section/objects_table/components/flyout.tsx

      Line 249 in 0f4319c

      legacyImport = async () => {

    • Remove legacyFileWarning and associated state:

      kibana/src/plugins/saved_objects_management/public/management_section/objects_table/components/flyout.tsx

      Line 866 in 0f4319c

      if (this.state.isLegacyFile) {

  • Remove all related functional tests for legacy imports:

    kibana/test/functional/apps/management/_import_objects.ts

    Line 214 in 0f4319c

    describe('.json file', () => {

• Remove unused legacy import code in src/plugins/saved_objects_management/public/lib
  • When removing logLegacyImport, also remove the associated server route /api/saved_objects/_log_legacy_import

    kibana/src/plugins/saved_objects_management/public/lib/log_legacy_import.ts

    Lines 11 to 13 in 0f4319c

    	export async function logLegacyImport(http: HttpStart) {
    	return http.post('/api/saved_objects/_log_legacy_import');
    	}

• Remove saved object loaders & associated code (see Decouple saved object management from SavedObjectLoader #67607)

[elasticmachine]

Pinging @elastic/kibana-core (Team:Core)

[jportner]

@TinaHeiligers does this issue include removing the legacy import HTTP route? The description makes it sound like we are only making UI changes. Are we keeping that route around??

Edit: I see that server side work is tracked in #41439, and it appears from that issue description that the API will be sticking around. (for others reading this comment who may be unfamiliar, "legacy import" == "dashboard import")

Edit 2: based on #41439 (comment) it sounds like we are actually going to start collecting usage data in 7.16 but go ahead and remove this API in 8.0, with the understanding that we may need to add it again if we get enough demand for it

[pgayvallet]

does this issue include removing the legacy import HTTP route?

Nope, the legacy (dashboard) import and the legacy import (format) are two distinct things. This issue is about removing support of the legacy import format from SOM, and #41439 is about the legacy dashboard import.

it sounds like we are actually going to start collecting usage data in 7.16 but go ahead and remove this API in 8.0, with the understanding that we may need to add it again if we get enough demand for it

That's correct.