feat: Add bot API endpoint for reading room messages

Adds a new GET endpoint at /rooms/:room_id/:bot_key/messages that allows
bots to read messages from rooms they are members of.

The endpoint returns JSON with:
- Room info (id, name)
- Messages array with body (plain/html), created_at, and creator info
- Pagination info (oldest_id, newest_id, has_more)

Supports pagination via ?before=:id and ?after=:id query parameters,
consistent with the existing pagination in the messages controller.

This enables AI bots and other automated agents to understand conversation
context when responding to messages, rather than only receiving the single
message that triggered the webhook.

Co-authored-by: openhands <openhands@all-hands.dev>

test/controllers/messages/by_bots_controller_test.rb

@@ -51,8 +51,51 @@ class Messages::ByBotsControlleTest < ActionDispatch::IntegrationTest
     assert_response :redirect
   end
 
-  test "denied index" do
-    get room_messages_url(@room, bot_key: users(:bender).bot_key, format: :json)
+  test "index returns messages as JSON" do
+    get room_bot_messages_index_url(@room, users(:bender).bot_key)
+    assert_response :success
+
+    json = JSON.parse(response.body)
+    assert json["room"]["id"].present?
+    assert json["room"]["name"].present?
+    assert json["messages"].is_a?(Array)
+    assert json["pagination"].present?
+  end
+
+  test "index includes message details" do
+    # Create a message in the room first
+    post room_bot_messages_url(@room, users(:bender).bot_key), params: +"Test message for index"
+
+    get room_bot_messages_index_url(@room, users(:bender).bot_key)
+    assert_response :success
+
+    json = JSON.parse(response.body)
+    message = json["messages"].find { |m| m["body"]["plain"] == "Test message for index" }
+    assert message.present?, "Expected to find the test message"
+    assert message["id"].present?
+    assert message["created_at"].present?
+    assert message["creator"]["id"].present?
+    assert message["creator"]["name"].present?
+  end
+
+  test "index supports pagination with before parameter" do
+    get room_bot_messages_index_url(@room, users(:bender).bot_key, before: Message.last.id)
+    assert_response :success
+  end
+
+  test "index supports pagination with after parameter" do
+    get room_bot_messages_index_url(@room, users(:bender).bot_key, after: Message.first.id)
+    assert_response :success
+  end
+
+  test "index requires valid bot key" do
+    get room_bot_messages_index_url(@room, "invalid-bot-key")
+    assert_response :redirect  # Redirects to login
+  end
+
+  test "regular messages index still denied for bots" do
+    # The standard messages endpoint (not the bot-specific one) should still be forbidden
+    get room_messages_url(@room, bot_key: users(:bender).bot_key)
     assert_response :forbidden
   end
 end