Send an email when an account exists already

When you want to change your email address into an account which already exists, upstream sends an email to the existing account.
Lets do the same.

Kinda fixes #5630

Signed-off-by: BlackDex <black.dex@gmail.com>

src/api/core/accounts.rs

@@ -775,6 +775,11 @@ async fn post_email_token(data: Json<EmailTokenData>, headers: Headers, mut conn
     }
 
     if User::find_by_mail(&data.new_email, &mut conn).await.is_some() {
+        if CONFIG.mail_enabled() {
+            if let Err(e) = mail::send_change_email_existing(&data.new_email, &user.email).await {
+                error!("Error sending change-email-existing email: {e:#?}");
+            }
+        }
         err!("Email already in use");
     }
 

src/config.rs

@@ -1384,6 +1384,7 @@ where
     reg!("email/email_footer_text");
 
     reg!("email/admin_reset_password", ".html");
+    reg!("email/change_email_existing", ".html");
     reg!("email/change_email", ".html");
     reg!("email/delete_account", ".html");
     reg!("email/emergency_access_invite_accepted", ".html");

src/mail.rs

@@ -570,6 +570,20 @@ pub async fn send_change_email(address: &str, token: &str) -> EmptyResult {
     send_email(address, &subject, body_html, body_text).await
 }
 
+pub async fn send_change_email_existing(address: &str, acting_address: &str) -> EmptyResult {
+    let (subject, body_html, body_text) = get_text(
+        "email/change_email_existing",
+        json!({
+            "url": CONFIG.domain(),
+            "img_src": CONFIG._smtp_img_src(),
+            "existing_address": address,
+            "acting_address": acting_address,
+        }),
+    )?;
+
+    send_email(address, &subject, body_html, body_text).await
+}
+
 pub async fn send_test(address: &str) -> EmptyResult {
     let (subject, body_html, body_text) = get_text(
         "email/smtp_test",

src/static/templates/email/change_email_existing.hbs

@@ -0,0 +1,6 @@
+Your Email Change
+<!---------------->
+A user ({{ acting_address }}) recently tried to change their account to use this email address ({{ existing_address }}). An account already exists with this email ({{ existing_address }}).
+
+If you did not try to change an email address, contact your administrator.
+{{> email/email_footer_text }}

src/static/templates/email/change_email_existing.html.hbs

@@ -0,0 +1,16 @@
+Your Email Change
+<!---------------->
+{{> email/email_header }}
+<table width="100%" cellpadding="0" cellspacing="0" style="margin: 0; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; box-sizing: border-box; font-size: 16px; color: #333; line-height: 25px; -webkit-font-smoothing: antialiased; -webkit-text-size-adjust: none;">
+   <tr style="margin: 0; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; box-sizing: border-box; font-size: 16px; color: #333; line-height: 25px; -webkit-font-smoothing: antialiased; -webkit-text-size-adjust: none;">
+      <td class="content-block" style="font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; box-sizing: border-box; font-size: 16px; color: #333; line-height: 25px; margin: 0; -webkit-font-smoothing: antialiased; padding: 0 0 10px; -webkit-text-size-adjust: none; text-align: center;" valign="top" align="center">
+         A user ({{ acting_address }}) recently tried to change their account to use this email address ({{ existing_address }}). An account already exists with this email ({{ existing_address }}).
+      </td>
+   </tr>
+   <tr style="margin: 0; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; box-sizing: border-box; font-size: 16px; color: #333; line-height: 25px; -webkit-font-smoothing: antialiased; -webkit-text-size-adjust: none;">
+      <td class="content-block last" style="font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; box-sizing: border-box; font-size: 16px; color: #333; line-height: 25px; margin: 0; -webkit-font-smoothing: antialiased; padding: 0; -webkit-text-size-adjust: none; text-align: center;" valign="top" align="center">
+         If you did not try to change an email address, contact your administrator.
+      </td>
+   </tr>
+</table>
+{{> email/email_footer }}