prepare

func Prepare(
	r *gin.Engine,
	embeddedDiagrams bool,
	docStackName string,
	goModelsDir embed.FS,
	goDiagramsDir embed.FS,
	receivingAsSplitArea *split.AsSplitArea,
	map_GongStructName_InstancesNb map[string]int,
) (stager *models.Stager)