swagger-codegen: add page (#1727)

pages/common/swagger-codegen.md

@@ -0,0 +1,19 @@
+# swagger-codegen
+
+> Generate code and documentation for your REST api from a OpenAPI/swagger definition.
+
+- Generate documentation and code from an OpenAPI/swagger file:
+
+`swagger-codegen generate -i {{swagger_file}} -l {{language}}`
+
+- Generate java code using the library retrofit2 and the option useRxJava2:
+
+`swagger-codegen generate -i {{http://petstore.swagger.io/v2/swagger.json}} -l {{java}} --library {{retrofit2}} -D{{useRxJava2}}={{true}}`
+
+- List available languages:
+
+`swagger-codegen langs`
+
+- Display help options for the generate command:
+
+`swagger-codegen help {{generate}}`