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>

app/services/base_refresh_oauth_token_service.rb

@@ -0,0 +1,62 @@
+class BaseRefreshOauthTokenService
+  pattr_initialize [:channel!]
+
+  # Additional references: https://gitlab.com/gitlab-org/ruby/gems/gitlab-mail_room/-/blob/master/lib/mail_room/microsoft_graph/connection.rb
+  def access_token
+    return provider_config[:access_token] unless access_token_expired?
+
+    refreshed_tokens = refresh_tokens
+    refreshed_tokens[:access_token]
+  end
+
+  def access_token_expired?
+    expiry = provider_config[:expires_on]
+
+    return true if expiry.blank?
+
+    # Adding a 5 minute window to expiry check to avoid any race
+    # conditions during the fetch operation. This would assure that the
+    # tokens are updated when we fetch the emails.
+    Time.current.utc >= DateTime.parse(expiry) - 5.minutes
+  end
+
+  # Refresh the access tokens using the refresh token
+  # Refer: https://github.com/microsoftgraph/msgraph-sample-rubyrailsapp/tree/b4a6869fe4a438cde42b161196484a929f1bee46
+  def refresh_tokens
+    oauth_strategy = build_oauth_strategy
+    token_service = build_token_service(oauth_strategy)
+
+    new_tokens = token_service.refresh!.to_hash.slice(:access_token, :refresh_token, :expires_at)
+
+    update_channel_provider_config(new_tokens)
+    channel.reload.provider_config
+  end
+
+  def update_channel_provider_config(new_tokens)
+    channel.provider_config = {
+      access_token: new_tokens[:access_token],
+      refresh_token: new_tokens[:refresh_token],
+      expires_on: Time.at(new_tokens[:expires_at]).utc.to_s
+    }
+    channel.save!
+  end
+
+  private
+
+  def build_oauth_strategy
+    raise NotImplementedError
+  end
+
+  def provider_config
+    @provider_config ||= channel.provider_config.with_indifferent_access
+  end
+
+  # Builds the token service using OAuth2
+  def build_token_service(oauth_strategy)
+    OAuth2::AccessToken.new(
+      oauth_strategy.client,
+      provider_config[:access_token],
+      refresh_token: provider_config[:refresh_token]
+    )
+  end
+end

app/services/google/refresh_oauth_token_service.rb

@@ -0,0 +1,12 @@
+# Refer: https://learn.microsoft.com/en-us/entra/identity-platform/configurable-token-lifetimes
+class Google::RefreshOauthTokenService < BaseRefreshOauthTokenService
+  private
+
+  # Builds the OAuth strategy for Microsoft Graph
+  def build_oauth_strategy
+    app_id = GlobalConfigService.load('GOOGLE_OAUTH_CLIENT_ID', nil)
+    app_secret = GlobalConfigService.load('GOOGLE_OAUTH_CLIENT_SECRET', nil)
+
+    OmniAuth::Strategies::GoogleOauth2.new(nil, app_id, app_secret)
+  end
+end

app/services/imap/google_fetch_email_service.rb

@@ -0,0 +1,17 @@
+class Imap::GoogleFetchEmailService < Imap::BaseFetchEmailService
+  def fetch_emails
+    return if channel.provider_config['access_token'].blank?
+
+    fetch_mail_for_channel
+  end
+
+  private
+
+  def authentication_type
+    'XOAUTH2'
+  end
+
+  def imap_password
+    Google::RefreshOauthTokenService.new(channel: channel).access_token
+  end
+end

app/services/microsoft/refresh_oauth_token_service.rb

@@ -1,64 +1,9 @@
 # Refer: https://learn.microsoft.com/en-us/entra/identity-platform/configurable-token-lifetimes
-class Microsoft::RefreshOauthTokenService
-  pattr_initialize [:channel!]
-
-  # Additional references: https://gitlab.com/gitlab-org/ruby/gems/gitlab-mail_room/-/blob/master/lib/mail_room/microsoft_graph/connection.rb
-  def access_token
-    return provider_config[:access_token] unless access_token_expired?
-
-    refreshed_tokens = refresh_tokens
-    refreshed_tokens[:access_token]
-  end
-
-  def access_token_expired?
-    expiry = provider_config[:expires_on]
-
-    return true if expiry.blank?
-
-    # Adding a 5 minute window to expiry check to avoid any race
-    # conditions during the fetch operation. This would assure that the
-    # tokens are updated when we fetch the emails.
-    Time.current.utc >= DateTime.parse(expiry) - 5.minutes
-  end
-
-  # Refresh the access tokens using the refresh token
-  # Refer: https://github.com/microsoftgraph/msgraph-sample-rubyrailsapp/tree/b4a6869fe4a438cde42b161196484a929f1bee46
-  def refresh_tokens
-    oauth_strategy = build_oauth_strategy
-    token_service = build_token_service(oauth_strategy)
-
-    new_tokens = token_service.refresh!.to_hash.slice(:access_token, :refresh_token, :expires_at)
-
-    update_channel_provider_config(new_tokens)
-    channel.reload.provider_config
-  end
-
-  def update_channel_provider_config(new_tokens)
-    channel.provider_config = {
-      access_token: new_tokens[:access_token],
-      refresh_token: new_tokens[:refresh_token],
-      expires_on: Time.at(new_tokens[:expires_at]).utc.to_s
-    }
-    channel.save!
-  end
-
+class Microsoft::RefreshOauthTokenService < BaseRefreshOauthTokenService
   private
 
-  def provider_config
-    @provider_config ||= channel.provider_config.with_indifferent_access
-  end
-
   # Builds the OAuth strategy for Microsoft Graph
   def build_oauth_strategy
     ::MicrosoftGraphAuth.new(nil, GlobalConfigService.load('AZURE_APP_ID', ''), GlobalConfigService.load('AZURE_APP_SECRET', ''))
   end
-
-  # Builds the token service using OAuth2
-  def build_token_service(oauth_strategy)
-    OAuth2::AccessToken.new(
-      oauth_strategy.client,
-      provider_config[:access_token],
-      refresh_token: provider_config[:refresh_token]
-    )
-  end
 end