title: Angular i18n not supporting all locales in angular.json
body: <p>My angular application  I want to support languages french(Canada), french(France) and US english. This is my angular.json file i18n code.</p>
  <pre><code>&quot;i18n&quot;: {
          &quot;sourceLocale&quot;: &quot;en&quot;,
          &quot;locales&quot;: {
            &quot;fr-CA&quot;: &quot;src/locale/messages.fr-CA.xlf&quot;,
            &quot;fr-FR&quot;: &quot;src/locale/messages.fr-FR.xlf&quot;
          }
        }
  </code></pre>
  <p>Upon Building application (npm run build) I see  a message <strong>Locale data for 'fr-FR' cannot be found.  Using locale data for 'fr'.</strong></p>
  <ol>
  <li>Does this mean fr-FR is not allowed in angular.json, as it is not in ISO-639 list.</li>
  <li>Should I use <code>&quot;fr&quot;: &quot;src/locale/messages.fr.xlf&quot; </code> instead of fr-FR. Then should I match if the user in France (fr-FR locale) load code from  fr in dist folder.</li>
  <li>If '2' is wrong ignore the warning and as build producing fr-Fr specific application in dist folder use that.</li>
  <li>If  '2' is correct does that apply for all locales say use <em><strong>en</strong></em> for 'en-GB','en-CA'...</li>
  </ol>
  <p>I know there is something like registerLocaleData for displaying of dates and currency.</p>
  <pre><code>registerLocaleData(localeFr); 
  
  providers: [
      { provide: LOCALE_ID, useValue: 'fr-FR'},
    ]
  </code></pre>
  <p>I went over documentation few times <a href="https://angular.io/guide/i18n-overview" rel="nofollow noreferrer">https://angular.io/guide/i18n-overview</a>. I know I am missing something.</p>