feat: Add support for persistent copilot threads and messages (#11489)

The agents can see the previous conversations with the copilot if needed
with this change. We would have to cleanup the data after a while. For
now, that is not considered.

This PR adds:
- A new model for copilot_threads (intentionally named thread instead of
conversation to avoid confusion), copilot_messages
- Add the controller to fetch previous threads and messages.

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.0].define(version: 2025_04_21_085134) do
+ActiveRecord::Schema[7.0].define(version: 2025_05_12_231037) do
   # These extensions should be enabled to support this database
   enable_extension "pg_stat_statements"
   enable_extension "pg_trgm"
@@ -575,6 +575,31 @@ ActiveRecord::Schema[7.0].define(version: 2025_04_21_085134) do
     t.index ["waiting_since"], name: "index_conversations_on_waiting_since"
   end
 
+  create_table "copilot_messages", force: :cascade do |t|
+    t.bigint "copilot_thread_id", null: false
+    t.bigint "user_id", null: false
+    t.bigint "account_id", null: false
+    t.string "message_type", null: false
+    t.jsonb "message", default: {}, null: false
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["account_id"], name: "index_copilot_messages_on_account_id"
+    t.index ["copilot_thread_id"], name: "index_copilot_messages_on_copilot_thread_id"
+    t.index ["user_id"], name: "index_copilot_messages_on_user_id"
+  end
+
+  create_table "copilot_threads", force: :cascade do |t|
+    t.string "title", null: false
+    t.bigint "user_id", null: false
+    t.bigint "account_id", null: false
+    t.uuid "uuid", default: -> { "gen_random_uuid()" }, null: false
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["account_id"], name: "index_copilot_threads_on_account_id"
+    t.index ["user_id"], name: "index_copilot_threads_on_user_id"
+    t.index ["uuid"], name: "index_copilot_threads_on_uuid", unique: true
+  end
+
   create_table "csat_survey_responses", force: :cascade do |t|
     t.bigint "account_id", null: false
     t.bigint "conversation_id", null: false