fix: npm birthday

Replaces usage of flatOptions with npm.config.

lib/birthday.js

@@ -1,16 +1,9 @@
-class Birthday {
-  constructor (npm) {
-    this.npm = npm
-    Object.defineProperty(this.npm, 'flatOptions', {
-      value: {
-        ...npm.flatOptions,
-        package: ['@npmcli/npm-birthday'],
-        yes: true,
-      },
-    })
-  }
+const BaseCommand = require('./base-command.js')
 
+class Birthday extends BaseCommand {
   exec (args, cb) {
+    this.npm.config.set('package', ['@npmcli/npm-birthday'])
+    this.npm.config.set('yes', true)
     return this.npm.commands.exec(['npm-birthday'], cb)
   }
 }

test/lib/birthday.js

@@ -1,20 +1,23 @@
 const t = require('tap')
-const npm = {
-  flatOptions: {
-    yes: false,
-    package: [],
-  },
+const mockNpm = require('../fixtures/mock-npm')
+
+const config = {
+  yes: false,
+  package: [],
+}
+const npm = mockNpm({
+  config,
   commands: {
     exec: (args, cb) => {
-      t.equal(npm.flatOptions.yes, true, 'should say yes')
-      t.strictSame(npm.flatOptions.package, ['@npmcli/npm-birthday'],
+      t.equal(npm.config.get('yes'), true, 'should say yes')
+      t.strictSame(npm.config.get('package'), ['@npmcli/npm-birthday'],
         'uses correct package')
       t.strictSame(args, ['npm-birthday'], 'called with correct args')
       t.match(cb, Function, 'callback is a function')
       cb()
     },
   },
-}
+})
 
 const Birthday = require('../../lib/birthday.js')
 const birthday = new Birthday(npm)