Backport parameters for API::Parameters

This backports the EE specific parameters for API::Parameters, wrapping
them in a conditional.

lib/api/variables.rb

@@ -55,6 +55,10 @@ module API
         requires :key, type: String, desc: 'The key of the variable'
         requires :value, type: String, desc: 'The value of the variable'
         optional :protected, type: String, desc: 'Whether the variable is protected'
+
+        if Gitlab.ee?
+          optional :environment_scope, type: String, desc: 'The environment_scope of the variable'
+        end
       end
       post ':id/variables' do
         variable_params = declared_params(include_missing: false)
@@ -76,6 +80,10 @@ module API
         optional :key, type: String, desc: 'The key of the variable'
         optional :value, type: String, desc: 'The value of the variable'
         optional :protected, type: String, desc: 'Whether the variable is protected'
+
+        if Gitlab.ee?
+          optional :environment_scope, type: String, desc: 'The environment_scope of the variable'
+        end
       end
       # rubocop: disable CodeReuse/ActiveRecord
       put ':id/variables/:key' do