Step to reproduce:
1. Go to Developer menu -> Controls -> Stakeholders
2. Create a new stakeholder: enter Email of an existing stakeholder

Actual result:
The "Create" button is enabled but stakeholder creation fails with: "Request failed with status code 409"

Expected result:
The "Create" button should be disabled with an error under the Email field: "A stakeholder with this email address already exists. Please use a different email address."

Additional info:
The same error is displayed on the "Update stakeholder" wizard when trying to update the email with a value of an existing stakeholder