MM-10658 Change config fields to pointers (#9033)

* MM 10658 Change config fields to pointers (#8898)

* Change fields of config structs to pointers and set defaults

MM-10658 https://github.com/mattermost/mattermost-server/issues/8841

* Fix tests that go broken during switching config structs to pointers

MM-10658 https://github.com/mattermost/mattermost-server/issues/8841

* Apply changes of current master while switching config structs to pointers

MM-10658 https://github.com/mattermost/mattermost-server/issues/8841

* Fix new config pointer uses

* Fix app tests

* Fix mail test

* remove debugging statement

* fix TestUpdateConfig

* assign config consistently

* initialize AmazonS3Region in TestS3TestConnection

* initialize fields for TestEmailTest

* fix TestCheckMandatoryS3Fields

api4/file.go

@@ -600,7 +600,7 @@ func getFileLink(c *Context, w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	if !c.App.Config().FileSettings.EnablePublicLink {
+	if !*c.App.Config().FileSettings.EnablePublicLink {
 		c.Err = model.NewAppError("getPublicLink", "api.file.get_public_link.disabled.app_error", nil, "", http.StatusNotImplemented)
 		return
 	}
@@ -696,7 +696,7 @@ func getPublicFile(c *Context, w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	if !c.App.Config().FileSettings.EnablePublicLink {
+	if !*c.App.Config().FileSettings.EnablePublicLink {
 		c.Err = model.NewAppError("getPublicFile", "api.file.get_public_link.disabled.app_error", nil, "", http.StatusNotImplemented)
 		return
 	}