added some code based on the error message
added some code based on the error message

error message Unable to create an object of type 'MergeTemplateContext'. Add an implementation of 'IDesignTimeDbContextFactory<MergeTemplateContext>' to the project, or see https://go.microsoft.com/fwlink/?linkid=851728 for additional patterns supported at design time.

coe-google-apps-support/Mailman,coe-google-apps-support/Mailman,coe-google-apps-support/Mailman