DXCDT-234: Change ClientMetadata to *map[string]interface{}

[sergiught]

🔧 Changes

Changing the type of Client.ClientMetadata to *map[string]interface{} so we can send values as null, as that's the only way we can remove an old key from the map.

e.g. removing the "faa" key

POST /client
{
  "client_metadata": {
    "foo": "bar",
    "faa": "removeMe"
  }
}

PATCH /client
{
  "client_metadata": {
    "foo": "bar",
    "faa": null
  }
}

GET /client
{
  "client_metadata": {
    "foo": "bar"
  }
}

📚 References

🔬 Testing

📝 Checklist

• All new/changed/fixed functionality is covered by tests (or N/A)
• I have added documentation for all new/changed functionality (or N/A)