feat(webserver): Create template system for emails (#1447)

* feat(webserver): Create template system for emails

* Put newlines between lines of email body

* Move email template folder

ee/tabby-webserver/email_templates/invitation.html

@@ -0,0 +1,4 @@
+You've been invited to join a Tabby workspace!
+Welcome to Tabby! You have been invited to join a Tabby Server, where you can tap into AI-driven code completions and chat assistants.
+
+Go to {external_url}/auth/signup?invitationCode={code} to join!

ee/tabby-webserver/src/service/email.rs → ee/tabby-webserver/src/service/email/mod.rs

@@ -14,6 +14,7 @@ use lettre::{
 use tabby_db::{DbConn, DbEnum};
 use tokio::{sync::RwLock, task::JoinHandle};
 use tracing::warn;
+mod templates;
 
 use crate::schema::{
     email::{
@@ -223,11 +224,9 @@ impl EmailService for EmailServiceImpl {
     ) -> Result<JoinHandle<()>, SendEmailError> {
         let network_setting = self.db.read_network_setting().await?;
         let external_url = network_setting.external_url;
-        self.send_email_in_background(
-            email,
-            "You've been invited to join a Tabby workspace!".into(),
-            format!("Welcome to Tabby! You have been invited to join a Tabby Server, where you can tap into AI-driven code completions and chat assistants.\n\nGo to {external_url}/auth/signup?invitationCode={code} to join!"),
-        ).await
+        let contents = templates::invitation_email(&external_url, &code);
+        self.send_email_in_background(email, contents.subject, contents.body)
+            .await
     }
 }
 

ee/tabby-webserver/src/service/email/templates.rs

@@ -0,0 +1,26 @@
+pub struct EmailContents {
+    pub subject: String,
+    pub body: String,
+}
+
+fn format_email(template: &'static str, replacements: &[(&str, &str)]) -> EmailContents {
+    let mut lines = template.lines();
+    let mut subject = lines
+        .next()
+        .expect("Email must have subject line")
+        .to_string();
+    let body: Vec<&str> = lines.collect();
+    let mut body = body.join("\n");
+    for (name, replacement) in replacements {
+        body = body.replace(name, replacement);
+        subject = subject.replace(name, replacement);
+    }
+    EmailContents { subject, body }
+}
+
+pub fn invitation_email(external_url: &str, code: &str) -> EmailContents {
+    format_email(
+        include_str!("../../../email_templates/invitation.html"),
+        &[("{external_url}", external_url), ("{code}", code)],
+    )
+}