Workspaces changes the way to test APIs with a subscription key

**Describe the bug**
After creating a new APIM instance and testing the Echo API, subscription keys cannot be fetched automatically now.

**To Reproduce**
Steps to reproduce the behavior:

1. Deploy new API Management instance
2. Go to 'APIs'
3. Click on 'Echo API'
4. Click on 'Test' tab
5. See error

**Expected behavior**
We should be able to document how to easily test the Echo API.

**Screenshots**