feat: stringify object values (#24)

Fixes RM-2228
:---:

## 🧰 What's being changed?

Allow using objects as variable values.

__tests__/index.test.jsx

@@ -47,6 +47,12 @@ describe('single variable', () => {
   });
 
   it.todo('should set `selected` if nothing is selected');
+
+  it('should render objects as strings', () => {
+    const variable = shallow(<Variable {...props} user={{ apiKey: { renderTo: 'string' } }} />);
+
+    expect(variable.text()).toBe(JSON.stringify({ renderTo: 'string' }));
+  });
 });
 
 describe('multiple variables', () => {

index.jsx

@@ -33,9 +33,9 @@ class Variable extends React.Component {
   // - uppercase key
   getValue() {
     const { variable } = this.props;
-    if (this.props.user[variable]) return this.props.user[variable];
+    const value = this.props.user[variable] || this.getDefault();
 
-    return this.getDefault();
+    return typeof value === 'object' ? JSON.stringify(value) : value;
   }
 
   toggleVarDropdown() {