feat: register schemas with an identifier

Author: MaggieKimani1

src/Microsoft.OpenApi/Reader/ParseNodes/MapNode.cs

@@ -156,6 +156,16 @@ public override string GetRaw()
             return refNode?.GetScalarValue();
         }
 
+        public string? GetJsonSchemaIdentifier()
+        {
+            if (!_node.TryGetPropertyValue("$id", out JsonNode? idNode))
+            {
+                return null;
+            }
+
+            return idNode?.GetScalarValue();
+        }
+
         public string? GetSummaryValue()
         {
             if (!_node.TryGetPropertyValue("summary", out JsonNode? summaryNode))

src/Microsoft.OpenApi/Reader/V31/OpenApiSchemaDeserializer.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Microsoft Corporation. All rights reserved.
+// Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT license.
 
 using Microsoft.OpenApi.Extensions;
@@ -363,6 +363,7 @@ public static IOpenApiSchema LoadSchema(ParseNode node, OpenApiDocument hostDocu
             var mapNode = node.CheckMapNode(OpenApiConstants.Schema);
 
             var pointer = mapNode.GetReferencePointer();
+            var identifier = mapNode.GetJsonSchemaIdentifier();
 
             if (pointer != null)
             {
@@ -397,6 +398,12 @@ public static IOpenApiSchema LoadSchema(ParseNode node, OpenApiDocument hostDocu
                 schema.Extensions.Remove(OpenApiConstants.NullableExtension);
             }
 
+            if (identifier is not null && hostDocument.Workspace is not null)
+            {
+                // register the schema in our registry using the identifer's URL
+                hostDocument.Workspace.RegisterComponentForDocument(hostDocument, schema, identifier);
+            }
+
             return schema;
         }
     }