deviseでログインするパスワードを違うカラムに変更したいです

前提・実現したいこと

deviseで作成されるパスワードを別（管理者側）で作成してそれをユーザーがログインする際（sessions/new)のパスワードに割り当てたい。deviseのragistrations/newは使用しない。

ここに質問の内容を詳しく書いてください。
今回、ユーザーの登録は管理者側で行いたい。アドレスやパスワードはdeviseのコントローラーを使わずに管理者のコントローラーでユーザーを作成する。その作成したパスワードとemailでログインできる様にしたい。

該当のソースコード

schea.rb

 create_table "shops", force: :cascade do |t|
    t.string "email", default: "", null: false
    t.string "encrypted_password", default: "", null: false
    t.string "reset_password_token"
    t.datetime "reset_password_sent_at"
    t.datetime "remember_created_at"
    t.string "name", null: false
    t.string "phonenumber", null: false
    t.string "address", null: false
    t.string "shop_image_id"
    t.string "postal_code", null: false
    t.string "open_time", null: false
    t.string "close_time", null: false
    t.string "lunch_limit"
    t.string "dinner_limit"
    t.float "latitude"
    t.float "longitude"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.string "password_digest"
    t.index ["email"], name: "index_shops_on_email", unique: true
    t.index ["reset_password_token"], name: "index_shops_on_reset_password_token", unique: true
  end

app/models/shop.rb

class Shop < ApplicationRecord
  # Include default devise modules. Others available are:
  # :confirmable, :lockable, :timeoutable, :trackable and :omniauthable
  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :validatable


         has_many :informations, dependent: :destroy
         has_many :reviews, dependent: :destroy
         has_many :favorites, dependent: :destroy
         has_many :inquiries, dependent: :destroy
         has_many :courses, dependent: :destroy
         has_many :messages, dependent: :destroy
         has_many :rooms, dependent: :destroy
         has_many :genres, dependent: :destroy
         has_many :shop_genres, through: :genres
         attr_accessor :shop_genre_ids
         has_secure_password

         attachment :shop_image
end

controllers/admins/shops_controller.rb

def new
    @shop = Shop.new
    @genres = Genre.all
  end

  def create
    @shop = Shop.new(shop_params)
    @shop_genres = Shop.all
    binding.pry
    if @shop.save
       shop_params[:shop_genre_ids].each_with_index do | genre, i |
        if i == 0
          next
        end
        genre = Genre.new(shop_genre_id: genre.to_i)
        genre.shop_id = @shop.id
        genre.save
    end
        redirect_to admins_shops_path(@shop)
    else
       render 'new'
    end
  end

view/admins/shops/new.html.erb

<%= form_for(@shop, url:admins_shops_path(@shop),method: :post) do |f| %>
	<div class = "food">
		<div class="field">
			<%= attachment_image_tag @shop, :shop_image, src: "", id:"img_prev", size: "200x200", alt:"Image preview", class: "item_prev", fallback: "no_image.jpg" %>
		</div>
	 	<div class="field">
			<%= f.label :shop_image,"image change" ,class: "btn btn-warning btn-lg" ,for:"post_img"%>
			<%= f.attachment_field :shop_image, id:"post_img", class: "image", style:"display:none;" %>
		</div>
		<div class="field">
			<%= f.label :email, "ショップ名" %><br />
			<%= f.text_field :email %>
		</div>
		<div class="field">
			<%= f.label :email, "メールアドレス" %><br />
			<%= f.text_field :email %>
		</div>
	 	<div class="field">
			<%= f.label :password_digest, "パスワード" %><br />
			<%= f.text_field :password_digest %>
		</div>
		<div class="field">
			<%= f.label :phonenumber, "電話番号" %><br />
			<%= f.telephone_field :phonenumber %>
		</div>
		<div class="field">
			<%= f.label :postal_code, "郵便番号" %><br />
			<%= f.number_field :postal_code %><span class="unit"></span>
		</div>
		<div class="field">
			<%= f.label :address, "住所"%><br />
			<%= f.text_field :address %>
		</div>
		<div class="field">
			<%= f.label :open_time, "開店時間" %><br />
			<%= f.text_field :open_time %>
		</div>
		<div class="field">
			<%= f.label :close_time, "閉店時間" %><br />
			<%= f.text_field :close_time %>
		</div>
		<div class="field">
			<%= f.label :lunch_limit, "ランチラストオーダー" %><br />
			<%= f.text_field :lunch_limit %>
		</div>
		<div class="field">
			<%= f.label :dinner_limit, "ディナーラストオーダー" %><br />
			<%= f.text_field :dinner_limit %>
		</div>

		<div class="form-group">
		  <%= f.label :shop_genres, class:'control-label' %>
		    <div class="checkbox">
		      <%= collection_check_boxes(:shop, :shop_genre_ids, ShopGenre.all, :id, :name) do |f| %>
		        <%= f.label {f.check_box + f.text} %>
		      <% end %>
		    </div>
		</div>
		<div class="field">
			<%= f.submit "shop create", class: "new-btn" %>
		</div>
	</div>
<% end %>

routes.rb

devise_for :shops, controllers: {
    sessions: 'shops/sessions',
}

controllers/shops/sessions_controller.rb

# frozen_string_literal: true

class Shops::SessionsController < Devise::SessionsController
  prepend_before_action :require_no_authentication, only: [:new, :create]
  prepend_before_action :allow_params_authentication!, only: :create
  prepend_before_action :verify_signed_out_shop, only: :destroy
  prepend_before_action(only: [:create, :destroy]) { request.env["devise.skip_timeout"] = true }

  # GET /resource/sign_in
  def new
    self.resource = resource_class.new(sign_in_params)
    clean_up_passwords(resource)
    yield resource if block_given?
    respond_with(resource, serialize_options(resource))
  end

  # POST /resource/sign_in
  def create
    #元の認証ロジック
    #self.resource = warden.authenticate!(auth_options)

    #emailだけでログインできるように変更
    self.resource = Shop.where(:name => params[:shop]['email']).first

    set_flash_message(:notice, :signed_in) if is_flashing_format?
    sign_in(resource_name, resource)
    yield resource if block_given?
    respond_with resource, :location => after_sign_in_path_for(resource)
  end

  # DELETE /resource/sign_out
  def destroy
    signed_out = (Devise.sign_out_all_scopes ? sign_out : sign_out(resource_name))
    set_flash_message! :notice, :signed_out if signed_out
    yield if block_given?
    respond_to_on_destroy
  end

  protected

  def sign_in_params
    devise_parameter_sanitizer.sanitize(:sign_in)
  end

  def serialize_options(resource)
    methods = resource_class.authentication_keys.dup
    methods = methods.keys if methods.is_a?(Hash)
    methods << :password if resource.respond_to?(:password)
    { methods: methods, only: [:password] }
  end

  def auth_options
    { scope: resource_name, recall: "#{controller_path}#new" }
  end

  def translation_scope
    'devise.sessions'
  end

  private

  # Check if there is no signed in user before doing the sign out.
  #
  # If there is no signed in user, it will set the flash message and redirect
  # to the after_sign_out path.
  def verify_signed_out_shop
    if all_signed_out?
      set_flash_message! :notice, :already_signed_out

      respond_to_on_destroy
    end
  end

  def all_signed_out?
    shops = Devise.mappings.keys.map { |s| warden.shop(scope: s, run_callbacks: false) }

    shops.all?(&:blank?)
  end

  def respond_to_on_destroy
    # We actually need to hardcode this as Rails default responder doesn't
    # support returning empty response on GET request
    respond_to do |format|
      format.all { head :no_content }
      format.any(*navigational_formats) { redirect_to after_sign_out_path_for(resource_name) }
    end
  end
end

試したこと

パスワードを暗号化して保存できる様にpassword_digestというカラムをshopに持たせ、対象のモデルファイル（shop.rb)にhas_secure_passwordと記述。
暗号化のためのbcryptというGemを追加。

あとはdeviseのパスワードなしでログインさせるというqiitaの記事を参考にdeviseのルートを変更し任意のコントローラーを指定しその記述をemailだけでログインできる様に変更。
そこから管理者側で作成したpassword_digestと組み合わせてログインできる様にしたいが、どうすれば実装できるのか分からず、いろいろな記事を見て見ましたがdeviseに関しての理解が乏しくわかりませんでした。
分からなすぎて不安で眠れず、、、何かヒントが欲しいと思い質問させていただきました。
学習を初めて間も無く、初の質問でわかりにくい説明で申し訳ありませんがよろしくお願い申し上げます。