Adding the new search engine abstraction (#13304)

* WIP

* Adding bleve to go modules

* WIP

* Adding missing files from searchengine implementation

* WIP

* WIP

* WIP

* WIP

* WIP

* WIP

* User and channel indexing and searches implemented

* Make bleve tests run with in-memory indexes

* Implement post index and deletion tests

* Initial commits for the search layer

* Removing unnecesary indexing

* WIP

* WIP

* More fixes for tests

* Adding the search layer

* Finishing the migration of searchers to the layer

* Removing unnecesary code

* Allowing multiple engines active at the same time

* WIP

* Add simple post search

* Print information when using bleve

* Adding some debugging to understand better how the searches are working

* Making more dynamic config of search engines

* Add post search basics

* Adding the Purge API endpoint

* Fixing bleve config updates

* Adding missed file

* Regenerating search engine mocks

* Adding missed v5 to modules imports

* fixing i18n

* Fixing some test around search engine

* Removing all bleve traces

* Cleaning up the vendors directory and go.mod/go.sum files

* Regenerating timer layer

* Adding properly the license

* Fixing govet shadow error

* Fixing some tests

* Fixing TestSearchPostsFromUser

* Fixing another test

* Fixing more tests

* Fixing more tests

* Removing SearchEngine redundant text from searchengine module code

* Fixing some reindexing problems in members updates

* Fixing tests

* Addressing PR comments

* Reverting go.mod and go.sum

* Addressing PR comments

* Fixing tests compilation

* Fixing govet

* Adding search engine stop method

* Being more explicit on where we use includeDeleted

* Adding GetSqlSupplier test helper method

* Mocking elasticsearch start function

* Fixing tests

Co-authored-by: Miguel de la Cruz <miguel@mcrx.me>
Co-authored-by: mattermod <mattermod@users.noreply.github.com>

app/app.go

@@ -16,6 +16,7 @@ import (
 	"github.com/mattermost/mattermost-server/v5/model"
 	"github.com/mattermost/mattermost-server/v5/services/httpservice"
 	"github.com/mattermost/mattermost-server/v5/services/imageproxy"
+	"github.com/mattermost/mattermost-server/v5/services/searchengine"
 	"github.com/mattermost/mattermost-server/v5/services/timezones"
 	"github.com/mattermost/mattermost-server/v5/utils"
 )
@@ -38,7 +39,7 @@ type App struct {
 	cluster          einterfaces.ClusterInterface
 	compliance       einterfaces.ComplianceInterface
 	dataRetention    einterfaces.DataRetentionInterface
-	elasticsearch    einterfaces.ElasticsearchInterface
+	searchEngine     *searchengine.Broker
 	ldap             einterfaces.LdapInterface
 	messageExport    einterfaces.MessageExportInterface
 	metrics          einterfaces.MetricsInterface
@@ -202,8 +203,8 @@ func (a *App) Compliance() einterfaces.ComplianceInterface {
 func (a *App) DataRetention() einterfaces.DataRetentionInterface {
 	return a.dataRetention
 }
-func (a *App) Elasticsearch() einterfaces.ElasticsearchInterface {
-	return a.elasticsearch
+func (a *App) SearchEngine() *searchengine.Broker {
+	return a.searchEngine
 }
 func (a *App) Ldap() einterfaces.LdapInterface {
 	return a.ldap