adding dev guide for apig and fixing modelarts

otc_metadata/data/documents/apig-dev.yaml

@@ -0,0 +1,9 @@
+---
+hc_location: devg/apig
+html_location: docs/apig/dev
+link: /api-gateway/dev-guide/
+pdf_name: apig-dev-guide
+rst_location: dev_guide/source
+service_type: apig
+title: Developer Guide
+type: dev