Is your feature request related to a problem? Please describe.
In Decidim we have seen that there are two types of participants:

• One-time participants: Those who access once to perform a specific action (such as voting on participatory budgets) and do not return to the platform.
• Recurrent participants: Those participants who return more frequently to the platform to participate in different processes.

For one-time participants, it is usually frustrating to have to register to perform a single action that also requires verification. So they need to complete two forms to perform one action, sometimes these participants leaves the process uncomplete.

Describe the solution you'd like
I want a feature that enables direct verification without registration, so participants can complete an action without needing to register, just verifying themselves. This feature is designed for short periods of time and specific moments during a participatory process, specially for voting periods.

• This feature should work as a new verification method.
• This feature can be activated/deactivated in different components.
• In the system panel, I should be able to enable ephemeral-verification and link it to another existing verification method (i.e. organization census).
• To enable ephemeral-verification will be necessary to revoke all the verifications. By doing that, we are reducing the possible verifications conflicts that could emerge during the participatory action.

Alternatives

In Barcelona, they implemented the “ephemeral user)” feature, that was a similar approach to that.

Mokcup
Mobile

Does this issue could impact on users private data?
Yes. You are asking for personal data when they are verifying themselves.

Acceptance criteria

• Given I’m a system admin
  When I go to /system
  Then I can enable the method “Ephemeral Verification” and choose a verification method already enabled.
• Given I’m an admin
  When I want to enable permissions in a component
  Then I can select the method “Ephemeral Verification”
• Given I’m an admin
  When I want to enable “Ephemeral verification” in a component
  Then I’m prompted with a modal saying that “In order to enable this authorisation method, you need to revoke all of the existing authorizations. This minimises the risk of verification conflicts.”
  This modal should have a CTA to “Revoke all verifications”.
• Given I’m an admin
  When I enable the method “Ephemeral Verification” in a component,
  Then the permissions apply for that component action.

Flow 1) Visitant

• Given I’m a visitant
  When I want to make an action restricted by the “Ephemeral Verification” method
  Then I’m prompted directly with the verification form.
• Given I’m a visitant
  When I have completed the verification process
  Then an ephemeral session is created.
• Given I’m a visitant
  When I have completed the verification process
  Then I gain access to the action.
• Given I’m an ephemeral user
  When I leave uncomplete the action
  Then the ephemeral session is automatically closed after XX minutes. (according to session expiration time defined)
• Given I’m an ephemeral user
  When I want to quit the component with permisions enabled
  Then I’m prompted with a modal warning me that I will be logged out if I leave this page.
• Given I am a visitant with an existing ephemeral session
  When I attempt to verify myself again using my data that has already been used
  Then my existing ephemeral session is retrieved
  And I can view and edit my previous votes

Flow 2) Registered participant

• Given I’m a registered participant
  When I want to make an action restricted by the “Ephemeral Verification” method
  Then I’m prompted directly with the verification form.
• Given that I’m a registered participant, logged in
  When I click on an action restricted by “Ephemeral verification”
  Then I’m prompted directly with the verification form.
• Given that I’m a registered participant, logged in
  When I complete the authorization form
  Then, I’m verified and I gain access to the action
  And then, the verification is saved in my profile on /authorizations

Edge cases

• Given I am a visitant
  When I attempt to verify myself using the data of a registered participant who has already been verified
  Then a verification conflict occurs
  And I am prevented from proceeding
• Given I am an ephemeral user who has already voted
  When I register and try to verify myself with my information
  Then the data from the ephemeral user is retrieved and merged with the registered participant's account.
  And then I can see and edit my votes.

Retrocompatibilty

• Backport this PR to make it compatible with 0.29 version