Add Binance support, heavily inspired by the Coinbase one (#1317)

* feat: add Binance support (Items, Accounts, Importers, Processor, and Sync)

* refactor: deduplicate 'stablecoins' constant and push stale_rate filter to SQL

---------

Signed-off-by: Juan José Mata <juanjo.mata@gmail.com>
Co-authored-by: Juan José Mata <juanjo.mata@gmail.com>

test/controllers/binance_items_controller_test.rb

@@ -0,0 +1,184 @@
+require "test_helper"
+
+class BinanceItemsControllerTest < ActionDispatch::IntegrationTest
+  include ActiveJob::TestHelper
+
+  setup do
+    sign_in users(:family_admin)
+    @family = families(:dylan_family)
+    @binance_item = BinanceItem.create!(
+      family: @family,
+      name: "Test Binance",
+      api_key: "test_key",
+      api_secret: "test_secret"
+    )
+  end
+
+  test "should destroy binance item" do
+    assert_difference("BinanceItem.count", 0) do # doesn't delete immediately
+      delete binance_item_url(@binance_item)
+    end
+
+    assert_redirected_to settings_providers_path
+    @binance_item.reload
+    assert @binance_item.scheduled_for_deletion?
+  end
+
+  test "should sync binance item" do
+    post sync_binance_item_url(@binance_item)
+    assert_response :redirect
+  end
+
+  test "should show setup_accounts page" do
+    get setup_accounts_binance_item_url(@binance_item)
+    assert_response :success
+  end
+
+  test "complete_account_setup creates accounts for selected binance_accounts" do
+    binance_account = @binance_item.binance_accounts.create!(
+      name: "Spot Portfolio",
+      account_type: "spot",
+      currency: "USD",
+      current_balance: 1000.0
+    )
+
+    assert_difference "Account.count", 1 do
+      post complete_account_setup_binance_item_url(@binance_item), params: {
+        selected_accounts: [ binance_account.id ]
+      }
+    end
+
+    assert_response :redirect
+
+    binance_account.reload
+    assert_not_nil binance_account.current_account
+    assert_equal "Crypto", binance_account.current_account.accountable_type
+  end
+
+  test "complete_account_setup with no selection shows message" do
+    @binance_item.binance_accounts.create!(
+      name: "Spot Portfolio",
+      account_type: "spot",
+      currency: "USD",
+      current_balance: 1000.0
+    )
+
+    assert_no_difference "Account.count" do
+      post complete_account_setup_binance_item_url(@binance_item), params: {
+        selected_accounts: []
+      }
+    end
+
+    assert_response :redirect
+  end
+
+  test "complete_account_setup skips already linked accounts" do
+    binance_account = @binance_item.binance_accounts.create!(
+      name: "Spot Portfolio",
+      account_type: "spot",
+      currency: "USD",
+      current_balance: 1000.0
+    )
+
+    # Pre-link the account
+    account = Account.create!(
+      family: @family,
+      name: "Existing Binance",
+      balance: 1000,
+      currency: "USD",
+      accountable: Crypto.create!(subtype: "exchange")
+    )
+    AccountProvider.create!(account: account, provider: binance_account)
+
+    assert_no_difference "Account.count" do
+      post complete_account_setup_binance_item_url(@binance_item), params: {
+        selected_accounts: [ binance_account.id ]
+      }
+    end
+  end
+
+  test "cannot access other family's binance_item" do
+    other_family = families(:empty)
+    other_item = BinanceItem.create!(
+      family: other_family,
+      name: "Other Binance",
+      api_key: "other_test_key",
+      api_secret: "other_test_secret"
+    )
+
+    get setup_accounts_binance_item_url(other_item)
+    assert_response :not_found
+  end
+
+  test "link_existing_account links manual account to binance_account" do
+    manual_account = Account.create!(
+      family: @family,
+      name: "Manual Crypto",
+      balance: 0,
+      currency: "USD",
+      accountable: Crypto.create!(subtype: "exchange")
+    )
+
+    binance_account = @binance_item.binance_accounts.create!(
+      name: "Spot Portfolio",
+      account_type: "spot",
+      currency: "USD",
+      current_balance: 1000.0
+    )
+
+    assert_difference "AccountProvider.count", 1 do
+      post link_existing_account_binance_items_url, params: {
+        account_id: manual_account.id,
+        binance_account_id: binance_account.id
+      }
+    end
+
+    binance_account.reload
+    assert_equal manual_account, binance_account.current_account
+  end
+
+  test "link_existing_account rejects account with existing provider" do
+    linked_account = Account.create!(
+      family: @family,
+      name: "Already Linked",
+      balance: 0,
+      currency: "USD",
+      accountable: Crypto.create!(subtype: "exchange")
+    )
+
+    other_binance_account = @binance_item.binance_accounts.create!(
+      name: "Other Account",
+      account_type: "margin",
+      currency: "USD",
+      current_balance: 500.0
+    )
+    AccountProvider.create!(account: linked_account, provider: other_binance_account)
+
+    binance_account = @binance_item.binance_accounts.create!(
+      name: "Spot Portfolio",
+      account_type: "spot",
+      currency: "USD",
+      current_balance: 1000.0
+    )
+
+    assert_no_difference "AccountProvider.count" do
+      post link_existing_account_binance_items_url, params: {
+        account_id: linked_account.id,
+        binance_account_id: binance_account.id
+      }
+    end
+  end
+
+  test "select_existing_account renders without layout" do
+    account = Account.create!(
+      family: @family,
+      name: "Manual Account",
+      balance: 0,
+      currency: "USD",
+      accountable: Crypto.create!(subtype: "exchange")
+    )
+
+    get select_existing_account_binance_items_url, params: { account_id: account.id }
+    assert_response :success
+  end
+end