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/team.go

@@ -7,6 +7,7 @@ import (
 	"fmt"
 
 	"github.com/mattermost/platform/api"
+	"github.com/mattermost/platform/app"
 	"github.com/mattermost/platform/model"
 	"github.com/spf13/cobra"
 )
@@ -92,10 +93,8 @@ func createTeamCmdF(cmd *cobra.Command, args []string) error {
 		Type:        teamType,
 	}
 
-	c := getMockContext()
-	api.CreateTeam(c, team)
-	if c.Err != nil {
-		return errors.New("Team creation failed: " + c.Err.Error())
+	if _, err := app.CreateTeam(team); err != nil {
+		return errors.New("Team creation failed: " + err.Error())
 	}
 
 	return nil
@@ -156,7 +155,7 @@ func addUserToTeam(team *model.Team, user *model.User, userArg string) {
 		CommandPrintErrorln("Can't find user '" + userArg + "'")
 		return
 	}
-	if err := api.JoinUserToTeam(team, user); err != nil {
+	if err := app.JoinUserToTeam(team, user); err != nil {
 		CommandPrintErrorln("Unable to add '" + userArg + "' to " + team.Name)
 	}
 }