Fail vs. fatal on store startup (#24170)

If the store fails to initialize (e.g. run a migration), it would `log.Fatal` and then `os.Exit`. Unfortunately, this trips up `TestMain`, which happily keeps running tests, now guaranteed to fail.

Avoid this by instead returning an error from the store initialization, handling appropriately at the layer above.

server/cmd/mattermost/commands/db.go

@@ -113,7 +113,10 @@ func initDbCmdF(command *cobra.Command, _ []string) error {
 	}
 	defer configStore.Close()
 
-	sqlStore := sqlstore.New(configStore.Get().SqlSettings, nil)
+	sqlStore, err := sqlstore.New(configStore.Get().SqlSettings, nil)
+	if err != nil {
+		return errors.Wrap(err, "failed to initialize store")
+	}
 	defer sqlStore.Close()
 
 	CommandPrettyPrintln("Database store correctly initialised")

server/cmd/mattermost/commands/init.go

@@ -64,5 +64,5 @@ func initStoreCommandContextCobra(command *cobra.Command) (store.Store, error) {
 	}
 
 	config := cfgStore.Get()
-	return sqlstore.New(config.SqlSettings, nil), nil
+	return sqlstore.New(config.SqlSettings, nil)
 }