Add support for extra attributes oauth2 client

fields to create workforce pool operation. This
address the gap between newly added support in
Gcloud command of iam create workforce pool
provider and iam update workforce pool provider.

Fixes hashicorp/terraform-provider-google#20862

```
iam: added `extra_attributes_oauth2_client` field to `google_iam_workforce_pool_provider` SAML resource
```

Author: omkark-google

mmv1/products/iamworkforcepool/WorkforcePoolProvider.yaml

@@ -388,7 +388,7 @@ properties:
       The configuration for OAuth 2.0 client used to get the additional user
       attributes. This should be used when users can't get the desired claims
       in authentication credentials. Currently this configuration is only
-      supported with OIDC protocol.
+      supported with SAML and OIDC protocol.
     properties:
       - name: 'issuerUri'
         type: String

mmv1/templates/terraform/examples/iam_workforce_pool_provider_oidc_full.tf.tmpl

@@ -25,6 +25,19 @@ resource "google_iam_workforce_pool_provider" "{{$.PrimaryResourceId}}" {
       additional_scopes         = ["groups", "roles"]
     }
   }
+  extra_attributes_oauth2_client {
+    issuer_uri       = "https://login.microsoftonline.com/826602fe-2101-470c-9d71-ee1343668989/v2.0"
+    client_id        = "client-id"
+    client_secret {
+        value {
+          plain_text = "client-secret"
+        }
+      }
+    attributes_type = "AZURE_AD_GROUPS_MAIL"
+    query_parameters {
+        filter      = "mail:gcp"
+    }
+  }
   display_name        = "Display name"
   description         = "A sample OIDC workforce pool provider."
   disabled            = false

mmv1/templates/terraform/examples/iam_workforce_pool_provider_saml_full.tf.tmpl

@@ -14,6 +14,19 @@ resource "google_iam_workforce_pool_provider" "{{$.PrimaryResourceId}}" {
   saml {
     idp_metadata_xml  = "<?xml version=\"1.0\"?><md:EntityDescriptor xmlns:md=\"urn:oasis:names:tc:SAML:2.0:metadata\" entityID=\"https://test.com\"><md:IDPSSODescriptor protocolSupportEnumeration=\"urn:oasis:names:tc:SAML:2.0:protocol\"> <md:KeyDescriptor use=\"signing\"><ds:KeyInfo xmlns:ds=\"http://www.w3.org/2000/09/xmldsig#\"><ds:X509Data><ds:X509Certificate>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</ds:X509Certificate></ds:X509Data></ds:KeyInfo></md:KeyDescriptor><md:SingleSignOnService Binding=\"urn:oasis:names:tc:SAML:2.0:bindings:HTTP-Redirect\" Location=\"https://test.com/sso\"/></md:IDPSSODescriptor></md:EntityDescriptor>"
   }
+  extra_attributes_oauth2_client {
+    issuer_uri       = "https://login.microsoftonline.com/826602fe-2101-470c-9d71-ee1343668989/v2.0"
+    client_id        = "client-id"
+    client_secret {
+        value {
+          plain_text = "client-secret"
+        }
+      }
+    attributes_type = "AZURE_AD_GROUPS_MAIL"
+    query_parameters {
+        filter      = "mail:gcp"
+    }
+  }
   display_name        = "Display name"
   description         = "A sample SAML workforce pool provider."
   disabled            = false