Create the cost api for gcp:

url example:

• http://127.0.0.1:8000/api/cost-management/v1/reports/gcp/cost/
  • reporting_gcp_cost_summary

Lets start with the basic cost summary api with the provider_map & serializer combo. 
New files at:

• /koku/api/report/gcp/
  • _init_.py
  • provider_map.py
  • query_handler.py
  • serializers.py
  • view.py