Add support for secondary credentials for registration service

service/src/main/java/org/whispersystems/textsecuregcm/configuration/RegistrationServiceConfiguration.java

@@ -5,6 +5,7 @@ import javax.validation.constraints.NotBlank;
 public record RegistrationServiceConfiguration(@NotBlank String host,
                                                int port,
                                                @NotBlank String credentialConfigurationJson,
+                                               @NotBlank String secondaryCredentialConfigurationJson,
                                                @NotBlank String identityTokenAudience,
                                                @NotBlank String registrationCaCertificate) {
 }