email new teachers

app/controllers/Mod.scala

@@ -358,13 +358,16 @@ final class Mod(
         )
       ).bindFromRequest.fold(
         _ => BadRequest(html.mod.permissions(user)).fuccess,
-        permissions =>
+        permissions => {
+          val newPermissions = Permission(permissions) diff Permission(user.roles)
           modApi.setPermissions(AsMod(me), user.username, Permission(permissions)) >> {
-            (Permission(permissions) diff Permission(user.roles) contains Permission.Coach) ??
-              env.security.automaticEmail.onBecomeCoach(user)
+            newPermissions(Permission.Coach) ?? env.security.automaticEmail.onBecomeCoach(user)
+          } >> {
+            newPermissions(Permission.Coach) ?? env.security.automaticEmail.onBecomeTeacher(user)
           } >> {
             Permission(permissions).exists(_ is Permission.SeeReport) ?? env.plan.api.setLifetime(user)
           } inject redirect(user.username, true)
+        }
       )
     }
   }

modules/security/src/main/AutomaticEmail.scala

@@ -82,6 +82,32 @@ The lichess team
           text = s"""
 $body
 
+${Mailgun.txt.serviceNote}
+""",
+          htmlBody = standardEmail(body).some
+        )
+      }
+    }
+
+  def onBecomeTeacher(user: User)(implicit lang: Lang): Funit =
+    userRepo email user.id flatMap {
+      _ ?? { email =>
+        val body = s"""Hello,
+
+It is our pleasure to welcome you as a Lichess teacher.
+You can now create your first class on ${baseUrl}/class.
+
+Regards,
+
+The lichess team
+"""
+
+        mailgun send Mailgun.Message(
+          to = email,
+          subject = "Lichess Class feature unlocked",
+          text = s"""
+$body
+
 ${Mailgun.txt.serviceNote}
 """,
           htmlBody = standardEmail(body).some