Whatever I choose i have the message error as if I had chosen none.
<form class="HandleUsers__form" action="" method="post" @submit.prevent="addAdmin">
...
<div>
<legend>?????</legend>
<div>
<input type="radio" name="manager" value="manager" id="manager" v-model="role" required>
<label for="manager">Manager</label>
</div>
<div>
<input type="radio" name="author" value="author" id="author" v-model="role" required>
<label for="author">Author</label>
</div>
</div>
...
</form>
It's because they have different name
values, which creates two different radio groups.
A radio group is defined by giving each of radio buttons in the group the same name. Once a radio group is established, selecting any radio button in that group automatically deselects any currently-selected radio button in the same group.
Because your two inputs each have the same v-model but are in different groups, selecting a value for one group automatically deselects the value from the other group, generating your error since both groups are required.
Solution: If a user is meant to choose between Manager OR Author than they should be in the same group, i.e. they should have the same name
value.
<input type="radio" name="someGroup" value="manager" id="manager" v-model="role" required>
<input type="radio" name="someGroup" value="author" id="author" v-model="role" required>