Rails Devise Engine Sign_out link Error - ruby-on-rails

Question

I've installed devise on my engine and applied the following in my application.html.erb file:
<div id="user_nav">
<% if user_signed_in? %>
Signed in as <%= current_user.email %>. This cannot be cheese?
<%= link_to "Sign out", destroy_user_session_path, :method => :delete %>
<% else %>
<%= link_to 'Register', new_user_registration_path %> or <%= link_to 'Sign in', new_user_session_path %>
<% end %>
</div>
It shows No route matches "/users/sign_out" and it shows error for
<%= link_to 'Register', new_user_registration_path %> or <%= link_to 'Sign in', new_user_session_path %>
Error Message NameError in Devise::Sessions#new
undefined local variable or method `destroy_user_session_path' for #<#<Class:0x007fb4da2e9618>:0x007fb4da2db9a0>
Rake Routes Result
Routes for Fd::Engine:
users_auth_google_oauth2_callback GET /users/auth/google_oauth2/callback(.:format) fd/omniauth_callbacks#google_oauth2
fd_test_index GET /fd/test/index(.:format) fd/fd/test#index
fd_omniauth_callbacks_google_oauth2 GET /fd/omniauth_callbacks/google_oauth2(.:format) fd/fd/omniauth_callbacks#google_oauth2
new_user_session GET /users/sign_in(.:format) devise/sessions#new
user_session POST /users/sign_in(.:format) devise/sessions#create
destroy_user_session DELETE /users/sign_out(.:format) devise/sessions#destroy
user_password POST /users/password(.:format) devise/passwords#create
new_user_password GET /users/password/new(.:format) devise/passwords#new
edit_user_password GET /users/password/edit(.:format) devise/passwords#edit
PATCH /users/password(.:format) devise/passwords#update
PUT /users/password(.:format) devise/passwords#update
cancel_user_registration GET /users/cancel(.:format) devise/registrations#cancel
user_registration POST /users(.:format) devise/registrations#create
new_user_registration GET /users/sign_up(.:format) devise/registrations#new
edit_user_registration GET /users/edit(.:format) devise/registrations#edit
PATCH /users(.:format) devise/registrations#update
PUT /users(.:format) devise/registrations#update
DELETE /users(.:format) devise/registrations#destroy
user_omniauth_authorize GET|POST /users/auth/:provider(.:format) omniauth_callbacks#passthru {:provider=>/google_oauth2/}
user_omniauth_callback GET|POST /users/auth/:action/callback(.:format) omniauth_callbacks#(?-mix:google_oauth2)
fd_auth_index GET /fd/auth/index(.:format) fd/fd/auth#index
root GET / fd/auth#index
omniauth_callbacks_verify_otp GET /omniauth_callbacks/verify_otp(.:format) fd/omniauth_callbacks#verify_otp
omniauth_callbacks_delete_session GET /omniauth_callbacks/delete_session(.:format) fd/omniauth_callbacks#sign_out
Engine routes:
Fd::Engine.routes.draw do
devise_for :users,:controllers => { :omniauth_callbacks => "omniauth_callbacks" }, :class_name => "Fd::User", module: :devise
end

Answer 1

You Integrated OmniAuth in Devise, so if user gives correct credentials devise will create session , From your question i understand session is successfully created so if you want clear session just create a action in a controller(where you start session) and give
redirect_to "/users/sign_out"
or
try
redirect_to destroy_user_session_path
I hope this will work

Answer 2

Try this :
<%= link_to "Sign out", destroy_user_session_path, :method => :get %>
And make sure that you have below line in your config/initializers/devise.rb
config.sign_out_via = :get