Enabling IdWeb to use ExtraBodyParameters

Author: trwalke

src/Microsoft.Identity.Web.TokenAcquisition/TokenAcquisition.cs

@@ -643,6 +643,9 @@ public async Task<AuthenticationResult> GetAuthenticationResultForAppAsync(
                            tokenAcquisitionOptions.PopClaim!);
                     }
                 }
+
+                //Add extra body parameters configured by extensions
+                AddExtraBodyParametersIfNeeded(tokenAcquisitionOptions, builder);
             }
 
             try
@@ -676,6 +679,18 @@ public async Task<AuthenticationResult> GetAuthenticationResultForAppAsync(
             }
         }
 
+        private void AddExtraBodyParametersIfNeeded(TokenAcquisitionOptions tokenAcquisitionOptions, AcquireTokenForClientParameterBuilder builder)
+        {
+            if (tokenAcquisitionOptions.ExtraParameters != null
+                && tokenAcquisitionOptions.ExtraParameters.TryGetValue("EXTRA_BODY_PARAMETERS", out object? parameters))
+            {
+                if (parameters is Dictionary<string, Func<CancellationToken, Task<string>>> keyValuePairs)
+                {
+                    builder.WithExtraBodyParameters(keyValuePairs);
+                }
+            }
+        }
+
         private MergedOptions GetMergedOptions(string? authenticationScheme, TokenAcquisitionOptions? tokenAcquisitionOptions)
         {
             MergedOptions mergedOptions;