App Passwords: Improve validation and sanitization of the application name.

Application names are now required to be unique and cannot contain solely whitespace characters. Additionally, invalid characters are now stripped from the application name using `sanitize_text_field()`.

Props Boniu91, hellofromTonya, engahmeds3ed, xkon, francina.
Fixes #51941.


git-svn-id: https://develop.svn.wordpress.org/trunk@50030 602fd350-edb4-49c9-b593-d223f7449a82

src/js/_enqueues/admin/application-passwords.js

@@ -57,7 +57,7 @@
 			$newAppPassButton.prop( 'disabled', false );
 
 			$newAppPassForm.after( tmplNewAppPass( {
-				name: name,
+				name: response.name,
 				password: response.password
 			} ) );
 			$( '.new-application-password-notice' ).focus();

src/js/_enqueues/admin/auth-app.js

@@ -98,7 +98,7 @@
 					.append( '<p>' + wp.i18n.__( 'Be sure to save this in a safe location. You will not be able to retrieve it.' ) + '</p>' );
 
 				// We're using .text() to write the variables to avoid any chance of XSS.
-				$( 'strong', $notice ).text( name );
+				$( 'strong', $notice ).text( response.name );
 				$( 'input', $notice ).val( response.password );
 
 				$form.replaceWith( $notice );