Implement an admin dashboard

[marlabrizel]

Add a rudimentary admin dashboard to your Movies app. You should be able to flag a member as an admin, and should be forbidden from accessing the /admins/dashboards route unless logged in as an admin.

The following test cases should pass:

# test/system/admin_dashboards_system_test.rb

test "admins can access the admin dashboard" do
  admin = create(:member, password: "password", password_confirmation: "password", admin: true)

  visit movies_path
  click_link "Log In"
  fill_in :email, with: admin.email
  fill_in :password, with: "password"
  click_button "Submit"

  visit admin_dashboards_path
  
  assert_text "Welcome to the admin portal, #{admin.email}!"
end

test "non-admins cannot access the admin dashboard" do
  member = create(:member, password: "password", password_confirmation: "password", admin: false)

  visit movies_path
  click_link "Log In"
  fill_in :email, with: member.email
  fill_in :password, with: "password"
  click_button "Submit"

  visit admin_dashboards_path
  
  refute_text "Welcome to the admin portal, #{member.email}!"
  assert_text "Forbidden"
end