[CM] Soften response validation

[Dosant]

We started using content management for backward-compatibility reasons in appex analytics saved objects
Apart from other things the content management validate the responses against the schema, for example, for Discover's search:

kibana/src/plugins/saved_search/common/content_management/v1/cm_services.ts

Lines 21 to 67 in e4a088c

	const savedSearchAttributesSchema = schema.object(
	{
	title: schema.string(),
	sort: schema.oneOf([sortSchema, schema.arrayOf(sortSchema)]),
	columns: schema.arrayOf(schema.string()),
	description: schema.string(),
	grid: schema.object({
	columns: schema.maybe(
	schema.recordOf(
	schema.string(),
	schema.object({
	width: schema.maybe(schema.number()),
	})
	)
	),
	}),
	hideChart: schema.maybe(schema.boolean()),
	isTextBasedQuery: schema.maybe(schema.boolean()),
	usesAdHocDataView: schema.maybe(schema.boolean()),
	kibanaSavedObjectMeta: schema.object({
	searchSourceJSON: schema.string(),
	}),
	viewMode: schema.maybe(
	schema.oneOf([schema.literal('documents'), schema.literal('aggregated')])
	),
	hideAggregatedPreview: schema.maybe(schema.boolean()),
	rowHeight: schema.maybe(schema.number()),
	hits: schema.maybe(schema.number()),
	timeRestore: schema.maybe(schema.boolean()),
	timeRange: schema.maybe(
	schema.object({
	from: schema.string(),
	to: schema.string(),
	})
	),
	refreshInterval: schema.maybe(
	schema.object({
	pause: schema.boolean(),
	value: schema.number(),
	})
	),
	rowsPerPage: schema.maybe(schema.number()),
	breakdownField: schema.maybe(schema.string()),
	version: schema.maybe(schema.number()),
	},
	{ unknowns: 'forbid' }
	);

In case the response doesn't match the schema Discover and other appex analytics content storages throw an error:

kibana/packages/kbn-content-management-utils/src/saved_object_content_storage.ts

Lines 187 to 189 in 304cb25

	if (resultError) {
	throw Boom.badRequest(`Invalid response. ${resultError.message}`);
	}

We added schemas and response validation, but there are ways for saved objects to get into the system in a “unexpected” format, for example, we recently fixed a bug with discover's search sort field #166886. We fixed that particular bug, but there might be other similar bugs that are hard to find.

We agreed we should keep the validation error in dev and write warning in console in prod. Here is a possible approach we could take: #166919

cc @davismcphee

[elasticmachine]

Pinging @elastic/appex-sharedux (Team:SharedUX)