feat: IMAP Email Channel (#3298)

This change allows the user to configure both IMAP and SMTP for an email inbox. IMAP enables the user to see emails in Chatwoot. And user can use SMTP to reply to an email conversation.

Users can use the default settings to send and receive emails for email inboxes if both IMAP and SMTP are disabled.

Fixes #2520

app/mailers/conversation_reply_mailer_helper.rb

@@ -0,0 +1,51 @@
+module ConversationReplyMailerHelper
+  def prepare_mail(cc_bcc_enabled)
+    @options = {
+      to: @contact&.email,
+      from: email_from,
+      reply_to: email_reply_to,
+      subject: mail_subject,
+      message_id: custom_message_id,
+      in_reply_to: in_reply_to_email
+    }
+
+    if cc_bcc_enabled
+      @options[:cc] = cc_bcc_emails[0]
+      @options[:bcc] = cc_bcc_emails[1]
+    end
+
+    set_delivery_method
+    mail(@options)
+  end
+
+  private
+
+  def set_delivery_method
+    return unless @inbox.inbox_type == 'Email' && @channel.smtp_enabled
+
+    smtp_settings = {
+      address: @channel.smtp_address,
+      port: @channel.smtp_port,
+      user_name: @channel.smtp_email,
+      password: @channel.smtp_password,
+      domain: @channel.smtp_domain,
+      enable_starttls_auto: @channel.smtp_enable_starttls_auto,
+      authentication: @channel.smtp_authentication
+    }
+
+    @options[:delivery_method] = :smtp
+    @options[:delivery_method_options] = smtp_settings
+  end
+
+  def email_smtp_enabled
+    @inbox.inbox_type == 'Email' && @channel.imap_enabled
+  end
+
+  def email_from
+    email_smtp_enabled ? @channel.smtp_email : from_email_with_name
+  end
+
+  def email_reply_to
+    email_smtp_enabled ? @channel.smtp_email : reply_email
+  end
+end