Simplify account selection for member operations
When clicking the "certify" button, an empty modal is opened to select the account to use for certification emission.
Most of the time, less than one member account will be registered in the app, so the default behavior should be:
- if 0 identity is available → open instructions to register a member account or become member
- if 1 identity is available → use it for the certification without asking
- if more identities are available → warn the user that he should only be able to certify for himself, not his child or grandmother, and let him select the account