Multi version archive import (#2220)

* Fixed panic in PropDef.GetValue for `person` property types.
- the GetUserByID API can return a nil user and nil error

* return userid

* support old archive format

* move template init to app layer

* move app init

* init app

* revert

* ignore GetDefaultTemplate blocks call in store mock

* ignore GetDefaultTemplate blocks call in store mock2

* ignore InsertBlockss call in store mock3

* ignore RemoveDefaultTemplates call in store mock4

* ignore WriteFile call in files mock5

* ignore WriteFile call in files mock6

* ignore WriteFile call in files mock7

* ignore WriteFile call in files mock8

* fix unit tests

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

server/api/archive.go

@@ -9,6 +9,10 @@ import (
 	"github.com/mattermost/focalboard/server/services/audit"
 )
 
+const (
+	archiveExtension = ".boardarchive"
+)
+
 func (a *API) handleArchiveExport(w http.ResponseWriter, r *http.Request) {
 	// swagger:operation GET /api/v1/workspaces/{workspaceID}/archive/export archiveExport
 	//
@@ -64,7 +68,7 @@ func (a *API) handleArchiveExport(w http.ResponseWriter, r *http.Request) {
 		BoardIDs:    boardIDs,
 	}
 
-	filename := fmt.Sprintf("archive-%s.focalboard", time.Now().Format("2006-01-02"))
+	filename := fmt.Sprintf("archive-%s%s", time.Now().Format("2006-01-02"), archiveExtension)
 	w.Header().Set("Content-Type", "application/octet-stream")
 	w.Header().Set("Content-Disposition", "attachment; filename="+filename)
 	w.Header().Set("Content-Transfer-Encoding", "binary")