add automatically value to column database in rails

notes use rails 5.2 and postgresql

I have Foluser model contains name,email,password,id_watch

I need when admin add new foluser

1. generate password

   when admin create new foluser generate password like Secure Password Generator

2. get id_watch from admin model and put it to id_watch from Foluser model

   Adminwhen register enterusername,email,password,id_watch`

   in point 2 need take this id_watch and save it in user model .

admin only create foluser

`
class FolusersController < ApplicationController
  before_action :set_foluser, only: [:show, :edit, :update, :destroy]
  before_action :authenticate_user!, except: [:index, :show, :new , :create, :edit]

  # GET /folusers
  # GET /folusers.json
  def index
    @folusers = current_master.foluser.all

    #render json: @folusers

  end

  # GET /folusers/1
  # GET /folusers/1.json
  def show
    #@folusers = Foluser.where(master_id: @master.id).order("created_at DESC")

    #@foluser = Foluser.find(params[:id])
        #render json: @foluser



  end

  # GET /folusers/new
  def new
    @foluser = current_master.foluser.build
  end

  # GET /folusers/1/edit
  def edit
    #render json: @foluser
  end

  # POST /folusers
  # POST /folusers.json
  def create
    @foluser = current_master.foluser.build(foluser_params)


    respond_to do |format|
      if @foluser.save
        format.html { redirect_to @foluser, notice: 'Foluser was successfully created.' }
        format.json { render :show, status: :created, location: @foluser }
      else
        format.html { render :new }
        format.json { render json: @foluser.errors, status: :unprocessable_entity }
      end
    end
  end

  # PATCH/PUT /folusers/1
  # PATCH/PUT /folusers/1.json
  def update
    respond_to do |format|
      if @foluser.update(foluser_params)
        format.html { redirect_to @foluser, notice: 'Foluser was successfully updated.' }
        format.json { render :show, status: :ok, location: @foluser }
      else
        format.html { render :edit }
        format.json { render json: @foluser.errors, status: :unprocessable_entity }
      end
    end
  end

  # DELETE /folusers/1
  # DELETE /folusers/1.json
  def destroy
    @foluser.destroy
    respond_to do |format|
      format.html { redirect_to folusers_url, notice: 'Foluser was successfully destroyed.' }
      format.json { head :no_content }
    end
  end

  private
    # Use callbacks to share common setup or constraints between actions.
    def set_foluser
      @foluser = Foluser.find(params[:id])
    end

    # Never trust parameters from the scary internet, only allow the white list through.
    def foluser_params
      params.require(:foluser).permit(:name, :email, :numberphone, :password)
    end
end

foluser model

class Foluser < ApplicationRecord
    belongs_to :admin, :optional => true
end

admin model

class Master < ApplicationRecord

    has_many :foluser
end