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>

Makefile

@@ -201,8 +201,8 @@ endif
 
 app-layers: ## Extract interface from App struct
     # The following commented commands can be used to re-generate the AppIface from the App struct
-	# env GO111MODULE=off $(GO) get gopkg.in/reflog/struct2interface.v0
-	# $(GOBIN)/struct2interface.v0 -f "app" -o "app/app_iface.go" -p "app" -s "App" -i "AppIface" -t ./app/layer_generators/app_iface.go.tmpl
+	#env GO111MODULE=off $(GO) get gopkg.in/reflog/struct2interface.v0
+	#$(GOBIN)/struct2interface.v0 -f "app" -o "app/app_iface.go" -p "app" -s "App" -i "AppIface" -t ./app/layer_generators/app_iface.go.tmpl
 	$(GO) run ./app/layer_generators -in ./app/app_iface.go -out ./app/opentracing_layer.go -template ./app/layer_generators/opentracing_layer.go.tmpl
 
 i18n-extract: ## Extract strings for translation from the source code
@@ -234,6 +234,10 @@ einterfaces-mocks: ## Creates mock files for einterfaces.
 	env GO111MODULE=off $(GO) get -u github.com/vektra/mockery/...
 	$(GOBIN)/mockery -dir einterfaces -all -output einterfaces/mocks -note 'Regenerate this file using `make einterfaces-mocks`.'
 
+searchengine-mocks: ## Creates mock files for searchengines.
+	env GO111MODULE=off go get -u github.com/vektra/mockery/...
+	$(GOPATH)/bin/mockery -dir services/searchengine -all -output services/searchengine/mocks -note 'Regenerate this file using `make searchengine-mocks`.'
+
 pluginapi: ## Generates api and hooks glue code for plugins
 	$(GO) generate $(GOFLAGS) ./plugin