docs: initial auth troubleshooting docs

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

docs/auth/troubleshooting.md

@@ -0,0 +1,21 @@
+---
+id: troubleshooting
+title: Troubleshooting Auth
+description: Guidance for various issues that one might run into when setting up authentication
+---
+
+Auth is tricky and doesn't always work as expected. Below you'll find some of the common
+problems one might run into when setting up authentication, as well as some general
+troubleshooting tips.
+
+## Sign-in fails with "... provider is not configured to support sign-in"
+
+This happens if you try to sign in using an auth provider that has not been
+configured to allow sign-in. See the [Sign-in Identities and Resolvers](./identity-resolver.md)
+page for information about how to configure and customize sign-in.
+
+As part of the 1.1 release of Backstage we removed the default implementations
+of all sign-in resolvers. This was a necessary security fix as well as a step
+towards providing more clarity in the configuration of the sign-in process.
+You may encounter this error if you are upgrading from a previous version, in
+which case you would need to configure a sign-in resolver as described above.

microsite/sidebars.json

@@ -254,6 +254,7 @@
       "auth/auth-backend",
       "auth/oauth",
       "auth/auth-backend-classes",
+      "auth/troubleshooting",
       "auth/glossary"
     ],
     "Deployment": [

mkdocs.yml

@@ -157,6 +157,7 @@ nav:
       - Auth backend: 'auth/auth-backend.md'
       - OAuth and OpenID Connect: 'auth/oauth.md'
       - Auth backend classes: 'auth/auth-backend-classes.md'
+      - Troubleshooting Auth: 'auth/troubleshooting.md'
       - Glossary: 'auth/glossary.md'
   - Deployment:
       - Deploying Backstage: 'deployment/index.md'