FIX: Only check for conditional mediation when needed (#24142)

Some browsers still don't support conditional mediation. This PR fixes issues with:

- TOR browser (it doesn't have `PublicKeyCredential` at all)
- Firefox 119 (doesn't support conditional mediation)

We also need to make sure not to call `isConditionalMediationAvailable` on browsers that don't support the method but support the feature (like Safari on iOS).

app/assets/javascripts/discourse/app/components/modal/login.js

@@ -19,6 +19,7 @@ import escape from "discourse-common/lib/escape";
 import I18n from "discourse-i18n";
 
 export default class Login extends Component {
+  @service capabilities;
   @service dialog;
   @service siteSettings;
   @service site;
@@ -116,6 +117,22 @@ export default class Login extends Component {
   @action
   async passkeyLogin(mediation = "optional") {
     try {
+      // we need to check isConditionalMediationAvailable for Firefox
+      // without it, Firefox will throw console errors
+      // We cannot do a general check because iOS Safari and Chrome in Selenium quietly support the feature
+      // but they do not support the PublicKeyCredential.isConditionalMediationAvailable() method
+      if (
+        mediation === "conditional" &&
+        this.capabilities.isFirefox &&
+        window.PublicKeyCredential
+      ) {
+        const isCMA =
+          // eslint-disable-next-line no-undef
+          await PublicKeyCredential.isConditionalMediationAvailable();
+        if (!isCMA) {
+          return;
+        }
+      }
       const response = await ajax("/session/passkey/challenge.json");
 
       const publicKeyCredential = await getPasskeyCredential(

app/assets/javascripts/discourse/app/components/modal/login/local-login-form.js

@@ -36,15 +36,9 @@ export default class LocalLoginBody extends Component {
 
   @action
   passkeyConditionalLogin() {
-    if (
+    if (this.args.canUsePasskeys) {
-      // eslint-disable-next-line no-undef
+      this.args.passkeyLogin("conditional");
-      !PublicKeyCredential.isConditionalMediationAvailable ||
-      !this.args.canUsePasskeys
-    ) {
-      return;
     }
-
-    this.args.passkeyLogin("conditional");
   }
 
   @action