public Builder mergeIapCredential(
          com.google.cloud.websecurityscanner.v1.ScanConfig.Authentication.IapCredential value) {
        if (iapCredentialBuilder_ == null) {
          if (authenticationCase_ == 4
              && authentication_
                  != com.google.cloud.websecurityscanner.v1.ScanConfig.Authentication.IapCredential
                      .getDefaultInstance()) {
            authentication_ =
                com.google.cloud.websecurityscanner.v1.ScanConfig.Authentication.IapCredential
                    .newBuilder(
                        (com.google.cloud.websecurityscanner.v1.ScanConfig.Authentication
                                .IapCredential)
                            authentication_)
                    .mergeFrom(value)
                    .buildPartial();
          } else {
            authentication_ = value;
          }
          onChanged();
        } else {
          if (authenticationCase_ == 4) {
            iapCredentialBuilder_.mergeFrom(value);
          } else {
            iapCredentialBuilder_.setMessage(value);
          }
        }
        authenticationCase_ = 4;
        return this;
      }
<pre>
Authentication using Identity-Aware-Proxy (IAP).
</pre>

<code>
.google.cloud.websecurityscanner.v1.ScanConfig.Authentication.IapCredential iap_credential = 4;
</code>
java-websecurityscanner/proto-google-cloud-websecurityscanner-v1/src/main/java/com/google/cloud/websecurityscanner/v1/ScanConfig.java