feat: api validation by rules in apikana-defaults

Uses validatorjs to validate rules defined in apikana-defaults (under 'validation').
See the validatorjs documentation on how to define such rules.
The main intention behind this feature was to enforce the presence of
additional properties in an OpenAPI specification.

bin/apikana

@@ -133,6 +133,25 @@ function generate() {
         var plop = nodePlop(__dirname + '/../src/plopfile_start.js', { defaults });
         var generator = plop.getGenerator('start');
         const model = Object.assign({}, packageJSON, { api: openapi });
+
+        // Workaround for validatorjs to fix wildcard on `paths`
+        const paths = [];
+        Object.values(model.api.paths).forEach(path => paths.push(path));
+        model.api.paths = paths;
+
+        if (defaults.validation) {
+            const Validator = require('validatorjs')
+            const validator = new Validator(model.api, defaults.validation);
+            if(!validator.check()) {
+                log(colors.bold(colors.red('Validation of the OpenAPI definition has failed with ' + validator.errorCount + ' errors')));
+                Object.entries(validator.errors.all()).forEach(errorEntry => {
+                  const [errorField, error] = errorEntry;
+                  log(colors.bold(colors.red(errorField + ": " + error)))
+                });
+                process.exit(1);
+            }
+        }
+
         generator.runActions(model).then(_ => {
             require('../src/generate').generate(path.resolve(source), params.target());
         });