feat(change-email) [PM-30811]: Add feature flag. (#6969)

Author: enmande

src/Core/Constants.cs

@@ -168,6 +168,7 @@ public static class FeatureFlagKeys
     public const string SafariAccountSwitching = "pm-5594-safari-account-switching";
     public const string PM27086_UpdateAuthenticationApisForInputPassword = "pm-27086-update-authentication-apis-for-input-password";
     public const string PM27044_UpdateRegistrationApis = "pm-27044-update-registration-apis";
+    public const string ChangeEmailNewAuthenticationApis = "pm-30811-change-email-new-authentication-apis";
     public const string PM31088_MasterPasswordServiceEmitSalt = "pm-31088-master-password-service-emit-salt";
 
     /* Autofill Team */