MM-14145: The config store Set will now Save automatically (#10377)

* MM-14145: The config store Set will now Save automatically

When UpdateConfig (and configStore.Set) is called in admin.go and
config.go, commonStore.Set now takes a store-specific persist function.
It uses that persist function to save the configuration automatically.

Removed: Now callers do not have to call configStore.Save or
app.PersistConfig, and those functions have been removed.

Possible downside: this means a "failed to persist config" error can now
be thrown during a app.UpdateConfig or commonStore.Set call. But
considering application code never really sets a config without saving
it (except in the test cases, which were testing that -- see below), it
seems fine to group these responsibilities.

Also removed: tests for 'set without save'. Since that can not happen
anymore, the tests are not needed.

* Removed Save completely, cleaned up formatting, joined save test with
set tests.

* fixed shadowed variable error

app/admin.go

@@ -168,7 +168,6 @@ func (a *App) SaveConfig(newCfg *model.Config, sendConfigChangeClusterMessage bo
 		return model.NewAppError("saveConfig", "app.save_config.app_error", nil, err.Error(), http.StatusInternalServerError)
 	}
 
-	a.PersistConfig()
 	if a.Metrics != nil {
 		if *a.Config().MetricsSettings.Enable {
 			a.Metrics.StartServer()

app/config.go

@@ -56,12 +56,6 @@ func (a *App) UpdateConfig(f func(*model.Config)) {
 	a.Srv.UpdateConfig(f)
 }
 
-func (a *App) PersistConfig() {
-	if err := a.Srv.configStore.Save(); err != nil {
-		mlog.Error("Failed to persist config", mlog.Err(err))
-	}
-}
-
 func (s *Server) ReloadConfig() error {
 	debug.FreeOSMemory()
 	if err := s.configStore.Load(); err != nil {

app/saml.go

@@ -65,7 +65,6 @@ func (a *App) AddSamlPublicCertificate(fileData *multipart.FileHeader) *model.Ap
 	}
 
 	a.UpdateConfig(func(dest *model.Config) { *dest = *cfg })
-	a.PersistConfig()
 
 	return nil
 }
@@ -83,7 +82,6 @@ func (a *App) AddSamlPrivateCertificate(fileData *multipart.FileHeader) *model.A
 	}
 
 	a.UpdateConfig(func(dest *model.Config) { *dest = *cfg })
-	a.PersistConfig()
 
 	return nil
 }
@@ -101,7 +99,6 @@ func (a *App) AddSamlIdpCertificate(fileData *multipart.FileHeader) *model.AppEr
 	}
 
 	a.UpdateConfig(func(dest *model.Config) { *dest = *cfg })
-	a.PersistConfig()
 
 	return nil
 }
@@ -128,7 +125,6 @@ func (a *App) RemoveSamlPublicCertificate() *model.AppError {
 	}
 
 	a.UpdateConfig(func(dest *model.Config) { *dest = *cfg })
-	a.PersistConfig()
 
 	return nil
 }
@@ -147,7 +143,6 @@ func (a *App) RemoveSamlPrivateCertificate() *model.AppError {
 	}
 
 	a.UpdateConfig(func(dest *model.Config) { *dest = *cfg })
-	a.PersistConfig()
 
 	return nil
 }
@@ -166,7 +161,6 @@ func (a *App) RemoveSamlIdpCertificate() *model.AppError {
 	}
 
 	a.UpdateConfig(func(dest *model.Config) { *dest = *cfg })
-	a.PersistConfig()
 
 	return nil
 }