[MM-41576] Revamp database schema version (#19586)

* revamp db version and add applied migrations endpoint

* replace old schema version with new

* add db version subcommand

* add to local api

* reflect review comments

* log errors

* remove setting the version from model.CurrentVersion

* fix a test

app/server.go

@@ -20,6 +20,7 @@ import (
 	"os/exec"
 	"path"
 	"runtime"
+	"strconv"
 	"strings"
 	"sync"
 	"sync/atomic"
@@ -752,8 +753,8 @@ func (s *Server) Channels() *Channels {
 
 // Return Database type (postgres or mysql) and current version of Mattermost
 func (s *Server) DatabaseTypeAndMattermostVersion() (string, string) {
-	mattermostVersion, _ := s.Store.System().GetByName("Version")
-	return *s.Config().SqlSettings.DriverName, mattermostVersion.Value
+	schemaVersion, _ := s.Store.GetDBSchemaVersion()
+	return *s.Config().SqlSettings.DriverName, strconv.Itoa(schemaVersion)
 }
 
 // initLogging initializes and configures the logger(s). This may be called more than once.
@@ -2304,3 +2305,11 @@ func runDNDStatusExpireJob(a *App) {
 		}
 	})
 }
+
+func (a *App) GetAppliedSchemaMigrations() ([]model.AppliedMigration, *model.AppError) {
+	table, err := a.Srv().Store.GetAppliedMigrations()
+	if err != nil {
+		return nil, model.NewAppError("GetDBSchemaTable", "api.file.read_file.app_error", nil, err.Error(), http.StatusInternalServerError)
+	}
+	return table, nil
+}