feat(linear): Auto link Linear issues from private notes (#14405)

When an agent pastes a Linear issue URL into a private note on a
conversation, Chatwoot now links the issue to the conversation
automatically — no need to click "Link to Linear issue" first. The
standard activity message ("X linked Linear issue ABC-123") is posted
just like a manual link.

Fixes
[CW-7032](https://linear.app/chatwoot/issue/CW-7032/if-someone-post-a-linear-url-in-the-private-notes-automatically-link)

---------

Co-authored-by: Muhsin <12408980+muhsin-k@users.noreply.github.com>
Co-authored-by: Sojan Jose <sojan@pepalo.com>

lib/integrations/linear/auto_link_service.rb

@@ -0,0 +1,93 @@
+class Integrations::Linear::AutoLinkService
+  pattr_initialize [:account!, :message!]
+
+  LINEAR_URL_REGEX = %r{https?://linear\.app/[^/\s]+/issue/[A-Z][A-Z0-9_]+-\d+(?:/[^\s)]*)?}
+  IDENTIFIER_REGEX = %r{/issue/([A-Z][A-Z0-9_]+-\d+)}i
+  WORKSPACE_REGEX = %r{//linear\.app/([^/\s]+)/}i
+
+  def perform
+    return unless valid_message?
+
+    attempt_link
+  end
+
+  private
+
+  def valid_message?
+    message.private? && message.content.present? && message.sender.is_a?(User)
+  end
+
+  def attempt_link
+    linear_url = message.content[LINEAR_URL_REGEX]
+    return if linear_url.blank?
+
+    identifier = linear_url[IDENTIFIER_REGEX, 1]&.upcase
+    workspace = linear_url[WORKSPACE_REGEX, 1]&.downcase
+    return if identifier.blank? || workspace.blank? || already_linked?(identifier)
+
+    finalize_link(workspace, identifier)
+  end
+
+  def finalize_link(workspace, identifier)
+    node_id = resolve_node_id(workspace, identifier)
+    return if node_id.blank?
+    return unless link_to_linear(node_id, identifier)
+
+    post_activity_message(identifier)
+  end
+
+  def already_linked?(identifier)
+    response = processor.linked_issues(conversation_link)
+    return false if response[:error]
+
+    response[:data].any? { |attachment| attachment.dig('issue', 'identifier') == identifier }
+  end
+
+  def resolve_node_id(workspace, identifier)
+    response = processor.search_issue(identifier)
+    return if response[:error]
+
+    node = response[:data].find do |issue|
+      issue['identifier'] == identifier && node_workspace(issue) == workspace
+    end
+    node && node['id']
+  end
+
+  def node_workspace(node)
+    node['url']&.match(WORKSPACE_REGEX)&.[](1)&.downcase
+  end
+
+  def link_to_linear(node_id, identifier)
+    response = processor.link_issue(conversation_link, node_id, attachment_title, message.sender)
+    if response[:error].present?
+      Rails.logger.warn("[Linear::AutoLinkService] link_issue failed for #{identifier}: #{response[:error]}")
+      return false
+    end
+    true
+  end
+
+  def attachment_title
+    I18n.t(
+      'integration_apps.linear.attachment_link_title',
+      conversation_id: message.conversation.display_id,
+      name: message.conversation.contact&.name
+    )
+  end
+
+  def post_activity_message(identifier)
+    Linear::ActivityMessageService.new(
+      conversation: message.conversation,
+      action_type: :issue_linked,
+      user: message.sender,
+      issue_data: { id: identifier }
+    ).perform
+  end
+
+  def conversation_link
+    "#{ENV.fetch('FRONTEND_URL', nil)}/app/accounts/#{message.account_id}/conversations/#{message.conversation.display_id}"
+  end
+
+  def processor
+    @processor ||= Integrations::Linear::ProcessorService.new(account: account)
+  end
+end