use sql lower function

plume-models/src/email_signups.rs

@@ -132,7 +132,7 @@ impl EmailSignup {
 
     fn delete_existings_by_email(conn: &DbConn, email: &str) -> Result<usize> {
         let existing_signups = email_signups::table
-            .filter(email_signups::email.to_lowercase().eq(email.to_lowercase()));
+            .filter(lower(email_signups::email).eq(email.to_lowercase()));
         diesel::delete(existing_signups)
             .execute(&**conn)
             .map_err(Error::from)

plume-models/src/password_reset_requests.rs

@@ -24,8 +24,7 @@ impl PasswordResetRequest {
     pub fn insert(conn: &Connection, email: &str) -> Result<String> {
         // first, delete other password reset tokens associated with this email:
         let existing_requests = password_reset_requests::table.filter(
-            password_reset_requests::email
-                .to_lowercase()
+            lower(password_reset_requests::email)
                 .eq(email.to_lowercase()),
         );
         diesel::delete(existing_requests).execute(conn)?;

plume-models/src/users.rs

@@ -214,7 +214,7 @@ impl User {
         select(exists(
             users::table
                 .filter(users::instance_id.eq(Instance::get_local()?.id))
-                .filter(users::email.to_lowercase().eq(lower_email)),
+                .filter(lower(users::email).eq(lower_email)),
         ))
         .get_result(&**conn)
         .map_err(Error::from)