backend: add unique index on connections.name&path

twenty-backend/lib/twenty-backend/migration/3_add_unique_index_to_connections.rb

@@ -0,0 +1,9 @@
+class AddUniqueIndexToConnections < ActiveRecord::Migration[7.1]
+  def up
+    add_index :connections, [:name, :path], unique: true
+  end
+
+  def down
+    remove_index :connections, [:name, :path], unique: true
+  end
+end