feat: Add support for image files in Captain (#11730)

# Pull Request Template

## Linear links:
-
https://linear.app/chatwoot/issue/CW-4479/if-image-is-sent-by-the-customer-send-it-to-openai

## Description

This pull request adds “Captain image support” to Chatwoot. It
introduces multimodal message handling so that when a customer sends an
image, Captain can forward the file to OpenAI’s vision endpoint,
generate a caption/analysis
## Type of change

Please delete options that are not relevant.

- [x] New feature (non-breaking change which adds functionality)

## How Has This Been Tested?

<img width="891" alt="image"
src="https://github.com/user-attachments/assets/c7cc98ed-cc44-4865-a53a-83d129e2fe2c"
/>



## Checklist:

- [ ] My code follows the style guidelines of this project
- [ ] I have performed a self-review of my code
- [ ] I have commented on my code, particularly in hard-to-understand
areas
- [ ] I have made corresponding changes to the documentation
- [ ] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [ ] New and existing unit tests pass locally with my changes
- [ ] Any dependent changes have been merged and published in downstream
modules

---------

Co-authored-by: Pranav <pranav@chatwoot.com>

enterprise/app/services/captain/llm/assistant_chat_service.rb

@@ -12,9 +12,16 @@ class Captain::Llm::AssistantChatService < Llm::BaseOpenAiService
     register_tools
   end
 
-  def generate_response(input, previous_messages = [], role = 'user')
-    @messages += previous_messages
-    @messages << { role: role, content: input } if input.present?
+  # additional_message: A single message (String) from the user that should be appended to the chat.
+  #                    It can be an empty String or nil when you only want to supply historical messages.
+  # message_history:   An Array of already formatted messages that provide the previous context.
+  # role:              The role for the additional_message (defaults to `user`).
+  #
+  # NOTE: Parameters are provided as keyword arguments to improve clarity and avoid relying on
+  # positional ordering.
+  def generate_response(additional_message: nil, message_history: [], role: 'user')
+    @messages += message_history
+    @messages << { role: role, content: additional_message } if additional_message.present?
     request_chat_completion
   end
 

enterprise/app/services/captain/open_ai_message_builder_service.rb

@@ -0,0 +1,59 @@
+class Captain::OpenAiMessageBuilderService
+  pattr_initialize [:message!]
+
+  def generate_content
+    parts = []
+    parts << text_part(@message.content) if @message.content.present?
+    parts.concat(attachment_parts(@message.attachments)) if @message.attachments.any?
+
+    return 'Message without content' if parts.blank?
+    return parts.first[:text] if parts.one? && parts.first[:type] == 'text'
+
+    parts
+  end
+
+  private
+
+  def text_part(text)
+    { type: 'text', text: text }
+  end
+
+  def image_part(image_url)
+    { type: 'image_url', image_url: { url: image_url } }
+  end
+
+  def attachment_parts(attachments)
+    image_attachments = attachments.where(file_type: :image)
+    image_content = image_parts(image_attachments)
+
+    transcription = extract_audio_transcriptions(attachments)
+    transcription_part = text_part(transcription) if transcription.present?
+
+    attachment_part = text_part('User has shared an attachment') if attachments.where.not(file_type: %i[image audio]).exists?
+
+    [image_content, transcription_part, attachment_part].flatten.compact
+  end
+
+  def image_parts(image_attachments)
+    image_attachments.each_with_object([]) do |attachment, parts|
+      url = get_attachment_url(attachment)
+      parts << image_part(url) if url.present?
+    end
+  end
+
+  def get_attachment_url(attachment)
+    return attachment.external_url if attachment.external_url.present?
+
+    attachment.file.attached? ? attachment.file_url : nil
+  end
+
+  def extract_audio_transcriptions(attachments)
+    audio_attachments = attachments.where(file_type: :audio)
+    return '' if audio_attachments.blank?
+
+    audio_attachments.map do |attachment|
+      result = Messages::AudioTranscriptionService.new(attachment).perform
+      result[:success] ? result[:transcriptions] : ''
+    end.join
+  end
+end