posts and tags not working in Azure App Service

[thegrahamking]

I realise this isn't really a Statiq.Web issue but as it's based on the docs I thought someone might be able to help.

I'm running Statiq.Web using the CleanBlog theme on a Windows based Azure App Service.
I've added the web.config changes suggested in the docs for extensionless urls and in the main this is working, however, /tags and /posts are not working.

My output directory, and what's copied into the Azure App Service wwwroot folder contains something like this

.
├── posts/
│   └── 2021/
│       └── myblogpost.html
└── posts.html

If I go to mysite.com/posts/2021/myblogpost then the page loads fine but if I go to mysite.com/posts I get You do not have permission to view this directory or page.. If I go to mysite.com/posts.html (not what anything links to but just as a test) the page loads fine.

I'm guessing the issue is with the rewrite rules in IIS and the fact that there is a posts directory and a posts.html file in the same path.

Does anyone know how to get /posts internally redirecting to /posts.html? Thank you