feat: add Google Email fetch and OAuth token refresh service (#9603)

This PR adds the following changes

1. Add `Imap::GoogleFetchEmailService` and
`Google::RefreshOauthTokenService`. The
`Google::RefreshOauthTokenService` uses
`OmniAuth::Strategies::GoogleOauth2` which is already added as a packge
2. Update `Inboxes::FetchImapEmailsJob` to handle Google inboxes
3. Add SMTP settings for Google in `ConversationReplyMailerHelper` to
allow sending emails


## Preview

#### Incoming emails

![CleanShot 2024-06-06 at 17 17
22@2x](https://github.com/chatwoot/chatwoot/assets/18097732/9d7d70d1-68e3-4c16-b1ca-e5a2e6f890e8)

#### Outgoing email

![CleanShot 2024-06-06 at 17 18
05@2x](https://github.com/chatwoot/chatwoot/assets/18097732/1b4abf0e-e311-493e-bdc8-386886afbb25)

---------

Co-authored-by: Muhsin Keloth <muhsinkeramam@gmail.com>

spec/mailers/conversation_reply_mailer_spec.rb

@@ -283,6 +283,22 @@ RSpec.describe ConversationReplyMailer do
       end
     end
 
+    context 'when smtp enabled for google email channel' do
+      let(:ms_smtp_email_channel) do
+        create(:channel_email, imap_login: 'smtp@gmail.com',
+                               imap_enabled: true, account: account, provider: 'google', provider_config: { access_token: 'access_token' })
+      end
+      let(:conversation) { create(:conversation, assignee: agent, inbox: ms_smtp_email_channel.inbox, account: account).reload }
+      let(:message) { create(:message, conversation: conversation, account: account, message_type: 'outgoing', content: 'Outgoing Message 2') }
+
+      it 'use smtp mail server' do
+        mail = described_class.email_reply(message)
+        expect(mail.delivery_method.settings.empty?).to be false
+        expect(mail.delivery_method.settings[:address]).to eq 'smtp.gmail.com'
+        expect(mail.delivery_method.settings[:port]).to eq 587
+      end
+    end
+
     context 'when smtp disabled for email channel', :test do
       let(:conversation) { create(:conversation, assignee: agent, inbox: email_channel.inbox, account: account).reload }
       let(:message) { create(:message, conversation: conversation, account: account, message_type: 'outgoing', content: 'Outgoing Message 2') }

spec/models/channel/email_spec.rb

@@ -35,4 +35,15 @@ RSpec.describe Channel::Email do
       expect(channel.microsoft?).to be(true)
     end
   end
+
+  context 'when google?' do
+    it 'returns false' do
+      expect(channel.google?).to be(false)
+    end
+
+    it 'returns true' do
+      channel.provider = 'google'
+      expect(channel.google?).to be(true)
+    end
+  end
 end

spec/services/google/refresh_oauth_token_service_spec.rb

@@ -0,0 +1,89 @@
+require 'rails_helper'
+
+RSpec.describe Google::RefreshOauthTokenService do
+  let!(:google_channel) { create(:channel_email, :microsoft_email) }
+  let!(:google_channel_with_expired_token) do
+    create(
+      :channel_email, :microsoft_email, provider_config: {
+        expires_on: Time.zone.now - 3600,
+        access_token: SecureRandom.hex,
+        refresh_token: SecureRandom.hex
+      }
+    )
+  end
+
+  let(:new_tokens) do
+    {
+      access_token: SecureRandom.hex,
+      refresh_token: SecureRandom.hex,
+      expires_at: (Time.zone.now + 3600).to_i,
+      token_type: 'bearer'
+    }
+  end
+
+  context 'when token is not expired' do
+    it 'returns the existing access token' do
+      service = described_class.new(channel: google_channel)
+
+      expect(service.access_token).to eq(google_channel.provider_config['access_token'])
+      expect(google_channel.reload.provider_config['refresh_token']).to eq(google_channel.provider_config['refresh_token'])
+    end
+  end
+
+  describe 'on expired token or invalid expiry' do
+    before do
+      stub_request(:post, 'https://oauth2.googleapis.com/token').with(
+        body: { 'grant_type' => 'refresh_token', 'refresh_token' => google_channel_with_expired_token.provider_config['refresh_token'] }
+      ).to_return(status: 200, body: new_tokens.to_json, headers: { 'Content-Type' => 'application/json' })
+    end
+
+    context 'when token is invalid' do
+      it 'fetches new access token and refresh tokens' do
+        with_modified_env GOOGLE_OAUTH_CLIENT_ID: SecureRandom.uuid, GOOGLE_OAUTH_CLIENT_SECRET: SecureRandom.hex do
+          provider_config = google_channel_with_expired_token.provider_config
+          service = described_class.new(channel: google_channel_with_expired_token)
+          expect(service.access_token).not_to eq(provider_config['access_token'])
+
+          new_provider_config = google_channel_with_expired_token.reload.provider_config
+          expect(new_provider_config['access_token']).to eq(new_tokens[:access_token])
+          expect(new_provider_config['refresh_token']).to eq(new_tokens[:refresh_token])
+          expect(new_provider_config['expires_on']).to eq(Time.at(new_tokens[:expires_at]).utc.to_s)
+        end
+      end
+    end
+
+    context 'when expiry time is missing' do
+      it 'fetches new access token and refresh tokens' do
+        with_modified_env GOOGLE_OAUTH_CLIENT_ID: SecureRandom.uuid, GOOGLE_OAUTH_CLIENT_SECRET: SecureRandom.hex do
+          google_channel_with_expired_token.provider_config['expires_on'] = nil
+          google_channel_with_expired_token.save!
+          provider_config = google_channel_with_expired_token.provider_config
+          service = described_class.new(channel: google_channel_with_expired_token)
+          expect(service.access_token).not_to eq(provider_config['access_token'])
+
+          new_provider_config = google_channel_with_expired_token.reload.provider_config
+          expect(new_provider_config['access_token']).to eq(new_tokens[:access_token])
+          expect(new_provider_config['refresh_token']).to eq(new_tokens[:refresh_token])
+          expect(new_provider_config['expires_on']).to eq(Time.at(new_tokens[:expires_at]).utc.to_s)
+        end
+      end
+    end
+  end
+
+  context 'when refresh token is not present in provider config and access token is expired' do
+    it 'throws an error' do
+      with_modified_env GOOGLE_OAUTH_CLIENT_ID: SecureRandom.uuid, GOOGLE_OAUTH_CLIENT_SECRET: SecureRandom.hex do
+        google_channel.update(
+          provider_config: {
+            access_token: SecureRandom.hex,
+            expires_on: Time.zone.now - 3600
+          }
+        )
+
+        expect do
+          described_class.new(channel: google_channel).access_token
+        end.to raise_error(RuntimeError, 'A refresh_token is not available')
+      end
+    end
+  end
+end