PLT-4938 Add app package and move logic over from api package (#4931)

* Add app package and move logic over from api package

* Change app package functions to return errors

* Move non-api tests into app package

* Fix merge

cmd/platform/init.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 
 	"github.com/mattermost/platform/api"
+	"github.com/mattermost/platform/app"
 	"github.com/mattermost/platform/model"
 	"github.com/mattermost/platform/utils"
 	"github.com/spf13/cobra"
@@ -37,8 +38,8 @@ func initDBCommandContext(configFileLocation string) {
 
 	utils.ConfigureCmdLineLog()
 
-	api.NewServer()
-	api.InitStores()
+	app.NewServer()
+	app.InitStores()
 	if model.BuildEnterpriseReady == "true" {
 		api.LoadLicense()
 	}