docs: add more specific steps and information about oidc refresh tokens (#18336)

closes https://github.com/coder/coder/issues/18307

relates to https://github.com/coder/coder/pull/18318

preview:
-
[refresh-tokens](https://coder.com/docs/@18307-refresh-tokens/admin/users/oidc-auth/refresh-tokens)
-
[configuring-okta](https://coder.com/docs/@18307-refresh-tokens/tutorials/configuring-okta)
~(not sure why @Emyrk 's photo is so huge there though)~ ✔️
- [x] removed from
[idp-sync](https://coder.com/docs/@18307-refresh-tokens/admin/users/idp-sync)

to do:
- move keycloak
- add ping federate and azure
- edit text (possibly placeholders for now - I want to see how it all
relates and edit it again. right now, there's a note about the same
thing in every section in way that's not super helpful/necessary)
- ~convert some paragraphs to OL~ calling this out of scope for now

---------

Co-authored-by: EdwardAngert <17991901+EdwardAngert@users.noreply.github.com>

docs/admin/integrations/vault.md

@@ -19,7 +19,7 @@ will show you how to use these modules to integrate HashiCorp Vault with Coder.
 
 The [`vault-github`](https://registry.coder.com/modules/vault-github) module is a Terraform module that allows you to
 authenticate with Vault using a GitHub token. This module uses the existing
-GitHub [external authentication](../external-auth.md) to get the token and authenticate with Vault.
+GitHub [external authentication](../external-auth/index.md) to get the token and authenticate with Vault.
 
 To use this module, add the following code to your Terraform configuration.