[demolaf]

Restores the v15 email sign-up options: sign-up can ask for a name and save it as the display name, and apps can turn sign-up off. Builds on #1414, so custom email screens get the new fields before the slot API ships.

Changes

• withEmailSignIn(requireDisplayName:allowNewEmailAccounts:). requireDisplayName defaults to false so existing apps see no change (v15 and Android default to true); allowNewEmailAccounts defaults to true.
• EmailAuthContentState gains a displayName binding plus requiresDisplayName and canSignUp, all with init defaults. isValid needs a non-blank name on sign-up when one is required.
• The stock form shows a Name field on sign-up and hides the sign-up switch when sign-up is off. createUser(email:password:displayName:) saves the name before reporting the account signed in, and throws Firebase's own adminRestrictedOperation when sign-up is off, so AuthServiceError is unchanged.

API Usage

authService.withEmailSignIn(requireDisplayName: true, allowNewEmailAccounts: false)

EmailAuthScreen(flow: .signUp) { state in
  TextField("Email", text: state.email)
  if state.requiresDisplayName {
    TextField("Name", text: state.displayName)
  }
  SecureField("Password", text: state.password)
  SecureField("Confirm password", text: state.confirmPassword)
  Button("Create account", action: state.signUp)
    .disabled(!state.isValid || state.isLoading)
}

Preview

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Maintainer note: Fixes internal CPRN-638, fixes internal CPRN-639

[gemini-code-assist]

Code Review

This pull request introduces configuration options to control whether email sign-up requires a display name and whether new email accounts can be created. It updates AuthService with new parameters, adds a display name input field to the sign-up UI, introduces a new error case for disallowed sign-ups, and updates the corresponding tests and documentation. There are no review comments provided, so I have no additional feedback to offer.