Added 7.3 -> 7.4 upgrade guide

Author: wcabus

src/content/docs/identityserver/upgrades/index.md

@@ -16,6 +16,10 @@ changes. Some updates contain changes to the stores used by IdentityServer that
 schema updates. If you are using our Entity Framework based stores we recommend using Entity Framework
 Migrations.
 
+## Upgrading from version 7.3 to 7.4
+
+See [IdentityServer v7.3 to v7.4](/identityserver/upgrades/v7_3-to-v7_4.md).
+
 ## Upgrading from version 7.2 to 7.3
 
 See [IdentityServer v7.2 to v7.3](/identityserver/upgrades/v7_2-to-v7_3.md).

src/content/docs/identityserver/upgrades/v7_3-to-v7_4.md

@@ -0,0 +1,69 @@
+---
+title: "Duende IdentityServer v7.3 to v7.4"
+sidebar:
+  order: 26
+  label: v7.3 → v7.4
+---
+
+This upgrade guide covers upgrading from Duende IdentityServer v7.3 to v7.4 ([release notes](https://github.com/DuendeSoftware/products/releases/tag/is-7.4.0)).
+
+IdentityServer 7.4.0 is a significant release that includes:
+
+- Support for .NET 10
+- Support for OAuth 2.0 Authorization Server Metadata ([RFC 8414](https://www.rfc-editor.org/rfc/rfc8414.html))
+- New Callback option for path detection in Dynamic Providers
+- Improved UI locales support
+- Support for custom parameters in the Authorize Redirect Uri
+- Identity package now persists session claims based on an interface
+- Skipping front-channel logout iframe when unnecessary
+- Set HTTP activity name on routing
+
+There are no schema changes needed for IdentityServer 7.4. Small code changes maybe be required for some users to upgrade:
+
+- Removed the unused `Duende.IdentityServer.Models.DiscoveryDocument` class which was public
+- Marked static properties referring to counters in `Telemetry.cs` as `readonly`
+
+## Step 1: Update NuGet package
+
+In your IdentityServer host project, update the version of the NuGet.
+For example in your project file:
+
+```xml
+<PackageReference Include="Duende.IdentityServer" Version="7.3.0" />
+```
+
+would change to:
+
+```xml
+<PackageReference Include="Duende.IdentityServer" Version="7.4.0" />
+```
+
+## Step 2: Breaking Changes
+
+Small code changes maybe be required for some users to upgrade.
+
+#### Removed the unused `Duende.IdentityServer.Models.DiscoveryDocument` class which was public
+
+In the process of internal code cleanup, we found that the `Duende.IdentityServer.Models.DiscoveryDocument` class was 
+public but not used anywhere in the codebase. 
+
+If you were using this class in your codebase, you will need to replace it with your own implementation or use a 
+different class that provides similar functionality. You can find the removed class in the [pull request][1].
+
+https://github.com/DuendeSoftware/products/pull/2128
+
+#### Marked static properties referring to counters in `Telemetry.cs` as `readonly`
+
+In the process of internal code cleanup, these properties were updated to be marked as `readonly`. 
+Code should not have been updating these properties as it would likely change the behavior of the telemetry emitted by 
+IdentityServer. 
+
+Any code which was updating these properties should instead create its own counters for their specific scenario.
+
+https://github.com/DuendeSoftware/products/pull/2170
+
+## Step 3: Done!
+
+That's it. Of course, at this point you can and should test that your IdentityServer is updated and working properly.
+
+[1]: https://github.com/DuendeSoftware/products/pull/2128/files#diff-b9470315ba30a728f573d4fd52fae80da4f3f180b19d5e1b9b0bf3a9c7ce6841