Can not secure Consultations with verifiers

[Xfolchf]

Describe the bug
Consultations can not be configured with a Verifier to prevent unauthorized users to respond.

So right now any registered user can respond on all consultations. There is no way to require any type of verification.

Without the possibility of associating a verification system to a consultation the use of them is limited to private installations.

https://meta.decidim.org/processes/bug-report/f/210/proposals/12579

Extra data (please complete the following information):

• Device: [e.g. iPhone6, Desktop]
• Device OS: [e.g. iOS8.1, Windows 10]
• Browser: [e.g. Chrome, Firefox, Safari]
• Decidim Version: [e.g. 0.10] 0.11.x
• Decidim installation: [e.g. MetaDecidim]

Additional context
Add any other context about the problem here.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions. @carolromero & @xabier feel free to chime in.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions. @carolromero & @xabier feel free to chime in.