Devise params auto adds weird data in sign up registration controller - ruby-on-rails

Question

My application using vue3 to build devise sign up page and i'm using axios request to create user.
In registration controller, i found that params has added added an extra field name called registration data.
<ActionController::Parameters {"user"=>{"name"=>"name", "email"=>"mail", "phone"=>"123", "type"=>0}, "controller"=>"users/registrations", "action"=>"create", "registration"=>{"user"=>{"name"=>"name", "email"=>"mail", "phone"=>"123", "type"=>0}}}
It contains params[:user], that looks weird to me. Can someone explain?
"registration"=>{"user"=>{"name"=>"name", "email"=>"mail", "phone"=>"123", "type"=>0}
My form code:
methods: {
signUp: function(e) {
e.preventDefault();
let user_params = {
user: {
name: this.name,
email: this.email,
phone: this.phone,
type: this.type,
}
}
this.$http.post('/users', user_params)
.then(response => {
this.$emit('next');
}).catch(err => {
this.error = err.response.data;
});
},
}
And in view
<form>
<div class="col-md-6 col-sm-8 col-10 mt-5 mx-auto text-center">
<div class="checked-circle mx-auto">
<img :src="checkedStepImg" class="w-100 h-100">
</div>
<div class="title mt-5"> Let sign up for your account </div>
<div class="mt-3 text-red" v-if="error">{{ error }} </div>
<div class="row mt-3">
<div class="col-6">
<input class="form-control shadow-none rounded-0" placeholder="Name" v-model="name">
</div>
<div class="col-6">
<input class="form-control shadow-none rounded-0" placeholder="Email" v-model="email">
</div>
</div>
<div class="row mt-3">
<div class="col-6">
<div class="input-group">
<span class="input-group-text rounded-0">+1</span>
<input type="text" class="form-control shadow-none rounded-0 bg-white" placeholder="Phone" v-model="phone">
</div>
</div>
<div class="col-6">
<select class="form-select shadow-none rounded-0" aria-label="Default select example" v-model="type">
<option value="0" selected> Personal </option>
<option value="1"> Corporation </option>
</select>
</div>
</div>
<div class="col-6 col-sm-5 mx-auto btn-box mt-5">
<button class="btn btn-dark w-100 h-100" #click.prevent="signUp"> Sign up!</button>
</div>
</div>
</form>
That does not happen if i use a normal form devise sign_up