Add CIBA SVG diagram to documentation

Introduced a new SVG file illustrating the CIBA flow, placed under the documentation assets. This addition enhances the visual clarity and understanding of the CIBA process for readers.

Author: khalidabuhakmeh

src/content/docs/identityserver/fundamentals/users.md

@@ -58,7 +58,7 @@ If the user has never logged in there will be no cookie, and then the request to
 redirect to your login page. This is the entry point into your custom workflow that can take over to get the user logged
 in.
 
-![sign in flow](../ui/images/signin_flow.png)
+![sign in flow](../ui/images/signin_flow.svg)
 
 Once the login page has finished logging in the user with the ASP.NET Core authentication system, it will redirect the
 user back to the authorize endpoint.

src/content/docs/identityserver/ui/ciba.md

@@ -30,7 +30,7 @@ A nice feature of this workflow is that the user does not enter their credential
 
 Below is a diagram that shows the high level steps involved with the CIBA workflow and the supporting services involved.
 
-![Showing how CIBA works in diagram form](./images/ciba.png)
+![Showing how CIBA works in diagram form](./images/ciba.svg)
 
 
 * **Step 1**: IdentityServer exposes a [backchannel authentication request endpoint](/identityserver/reference/endpoints/ciba) that the client uses to initiate the CIBA workflow.

src/content/docs/identityserver/ui/federation.md

@@ -15,7 +15,7 @@ Federation means that your IdentityServer offers authentication methods that use
 If you offer a number of these external authentication methods, often the term *Federation Gateway* is used to describe
 this architectural approach.
 
-![Diagram showing the benefits of using a federation gateway](./images/federation.png)
+![Diagram showing the benefits of using a federation gateway](./images/federation.svg)
 
 Generally, this architecture allows shielding your client applications from the complexities of your authentication
 workflows and business requirements that go along with them.

src/content/docs/identityserver/ui/images/ciba.svg

@@ -21,7 +21,7 @@ The design goal of Duende IdentityServer is to provide a full implementation of
 
 To allow full flexibility of the UI, including business rules and user flow, the UI is separated from the core IdentityServer engine. The engine implements the endpoints specified in the protocols and hands off control to your code in the UI as necessary.
 
-![diagram showing how IdentityServer middleware is hosted in an ASP.NET Core application](./images/host.png)
+![diagram showing how IdentityServer middleware is hosted in an ASP.NET Core application](./images/host.svg)
 
 Our templates include a [quick start UI](/identityserver/quickstarts/2-interactive/#add-the-ui) and a [quick start UI adapted to ASP.NET Identity](/identityserver/quickstarts/5-aspnetid/) which provide a starting point for all the necessary pages, ready to be customized.