Add search engine support for files (#16190)

* Add search engine support for files

* Fixing i18n

* Fix golangci-lint

* Fix consistency problem in the Search receiver functio of the SqlFileStore

* Fixing some tests

* Fixing test

* Apply suggestions from code review

Co-authored-by: Mario de Frutos Dieguez <mario@defrutos.org>

* Addressing PR review comments

* Removing some empty lines

* Address PR review comments

* Fixing problem after merge master

* Fixing spelling problem

* Add missed translations

* Fixing certain global variable usages after merge master

* Fixing some constants usage

* Fixing goimports order

Co-authored-by: Mario de Frutos Dieguez <mario@defrutos.org>

model/post.go

@@ -164,6 +164,12 @@ type PostForIndexing struct {
 	ParentCreateAt *int64 `json:"parent_create_at"`
 }
 
+type FileForIndexing struct {
+	FileInfo
+	ChannelId string `json:"channel_id"`
+	Content   string `json:"content"`
+}
+
 // ShallowCopy is an utility function to shallow copy a Post to the given
 // destination without touching the internal RWMutex.
 func (o *Post) ShallowCopy(dst *Post) error {