Add slack link to confirmation email

app/views/devise/mailer/confirmation_instructions.html.erb

@@ -7,3 +7,5 @@ Confirm your membership with Ruby Australia.
 <p>To confirm both your email address and your membership for Ruby Australia, please follow the link below:</p>
 
 <p class="button"><%= link_to 'Confirm my membership', confirmation_url(@resource, confirmation_token: @token) %></p>
+
+<p>Once you've completed the confirmation above, be sure to join our Slack community at <%= link_to 'Slack', slack_url %>.</p>

spec/features/committee_manages_members_spec.rb

@@ -39,13 +39,15 @@
     expect(page).to have_content("Alex")
     expect(page).to have_content("Not yet")
 
+    last_year = Time.zone.today.year - 1
+
     click_link "Edit"
-    select "2019", from: "access_request_viewed_on_1i"
+    select last_year.to_s, from: "access_request_viewed_on_1i"
     select "December", from: "access_request_viewed_on_2i"
     select "31", from: "access_request_viewed_on_3i"
     click_button "Save"
 
     expect(page).to have_content("Alex")
-    expect(page).to have_content("2019-12-31")
+    expect(page).to have_content("#{last_year}-12-31")
   end
 end

spec/views/devise/mailer/confirmation_instructions.html.erb_spec.rb

@@ -0,0 +1,35 @@
+require 'rails_helper'
+
+RSpec.describe "devise/mailer/confirmation_instructions.html.erb", type: :view do
+  include Rails.application.routes.url_helpers
+
+  let(:user) { create(:user, full_name: "John Doe") }
+  let(:token) { "fake_token" }
+
+  before do
+    assign(:resource, user)
+    assign(:token, token)
+
+    render
+  end
+
+  it "displays the preheader text" do
+    expect(rendered).to include("Confirm my membership")
+  end
+
+  it "displays the welcome message with the user's full name" do
+    expect(rendered).to match(/Welcome John Doe!/)
+  end
+
+  it "displays the confirmation instructions" do
+    expect(rendered).to match(/To confirm both your email address and your membership for Ruby Australia, please follow the link below:/)
+  end
+
+  it "displays the confirmation link" do
+    expect(rendered).to have_link('Confirm my membership', href: user_confirmation_url(confirmation_token: token))
+  end
+
+  it "displays the Slack community invitation" do
+    expect(rendered).to have_link('Slack', href: slack_url)
+  end
+end