@MSWCRB To add your own oauth authentication to Swagger UI you need to modify openapi.json which is generated by ServiceStack.Api.OpenApi plugin and available if you point to http://yoursite.com/openapi URL. You need to add securityDefinitions object to this json and describe here how your authentication provider works. Here is the blog post which explains how security definitions can be configured for json file.
When you’ll get what need to be added to json file for describing your authentication schema, you can move these changes to auto-generated json which is available at /openapi path. To do this you need to add ApiDeclarationFilter which I mentioned in previous post and add OpenApiSecuritySchema in it which is mapped 1 to 1 from json definition you’ve got on previous step.