Updating multiple models with one form in Rails

Question

I am new to Rails and trying to build a form that allows users to complete and submit a form. The form completes their profile. I want the form to update the Users model (and database table) as well as the Interests model (hobbies). I am using a form with fields_for.

However submitting the form does not update the Interests model. It either only updates the User model or returns various errors (the following produces Interest user must exist error):

MODELS:

class User < ApplicationRecord
    has_many :interests, foreign_key: "interests_user_id"
    accepts_nested_attributes_for :interests
    
end

class Interest < ApplicationRecord
    belongs_to :user

    self.primary_key = "interest_id"

    
end

CONTROLLER:

class UsersController < ApplicationController
      
      def index
        @allUsers = User.all

      end

      def new
        @user = User.new
        @user.interests.build
        
      end

      def create
    @user = User.new permitted_params

    =begin
        @user = User.new(
                :author => params[:user][:author],
                :user_name => params[:user][:user_name],
                :user_bio => params[:user][:user_bio],
            )

    @user.interests.new(
      :interest_name => params[:user][:interests_attributes][:interest_name],
      :interest_experience_level => params[:user][:interests_attributes][:interest_experience_level],
      :interest_positon => params[:user][:interests_attributes][:interest_positon],


      )
    =end

        if @user.save
            redirect_to users_url

        else
            render 'new'

            end
            
          end
    
    
    
        private
    
            def permitted_params
              #params.require(:interest).permit(User.attribute_names.map(&:to_sym),interest.attribute_names.map(&:to_sym))
    
              params.require(:user).permit(User.attribute_names.map(&:to_sym), interests_attributes: [:interest_name,:interest_experience_level,:interest_positon])
    
    
            end
    
    end

FORM:

 <%= form_with model: @user do |newUser| %>
            <% if @user.errors.any? %>
                <ul>
                    <% @user.errors.full_messages.each do |message| %>
                        <li> <%= message %></li>
                    <%end%>
                </ul>
            <%end%>

            <div class="form-sections" id="user-profile">
                <h3>General Information</h3>
                <table class="formTables" id="formMainInfo">

                    <%= newUser.hidden_field :author, value:1 %>
                
                    <tr class="formRows">
                        <td class="formDescriptionCol"><%= newUser.label :user_name, "Your Name" %></td>
                        <td class="formInputCol">
                            <%= newUser.text_field :user_name %>
                        </td> 
                    </tr>
                    
                    
                    <tr class="formRows">
                        <td class="formDescriptionCol"> <%= newUser.label :user_bio, "Biography" %></td>
                        <td class="formInputCol">
                            <%= newUser.text_area :user_bio %>
                        </td> 
                    </tr>
                    
                    
                <h3>Interests</h3>


                    <%= newUser.fields_for :interests do |newInterest| %>
                        <tr class="interestRows">
                            <td >Interest Name:</td>
                            <td>
                                <%= newInterest.text_field :interest_name%>
                            </td> 
                        </tr>
                        <tr class="interestRows">
                            <td ><%=newInterest.label :interest_experience_level, "Experience Level" %></td>
                            <td >
                                <%= newInterest.text_field :interest_experience_level %>
                            </td> 
                        </tr>
                        <tr class="interestRows">
                            <td ><%= newInterest.label :interest_position, "Position" %></td>
                            <td >
                                <%= newInterest.text_field :interest_position %>
                            </td> 
                        </tr>
                        
                        
                    <%end%>
            
                </table>
            </div>
            
            <div class="formSections" id="buttonsSection">
                <%= newUser.submit "submit" %>
            </div>



        <%end%>

SCHEMA:

create_table "interests", primary_key: "interest_id", id: :integer, force: :cascade, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8" do |t|
    t.integer "interest_user_id", null: false
    t.string "interest_name", limit: 45, null: false
    t.string "interest_experience_level", limit: 45, null: false
    t.string "interest_position", limit: 45, null: false
    t.index ["interest_user_id"], name: "user_id_idx"
  end


create_table "users", primary_key: "user_id", id: :integer, force: :cascade, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8" do |t|
    t.string "user_name", limit: 60, null: false
    t.string "author", limit: 60, null: false
    t.string "user_bio", limit: 500, null: false
   
  end


  add_foreign_key "interests", "users", column: "interest_user_id", primary_key: "user_id", name: "interest_user_name", on_update: :cascade, on_delete: :cascade