feat: bit more robust register

src/commands/users.rs

@@ -10,17 +10,26 @@ pub async fn register(
     email: String,
 ) -> Result<(), Error> {
     if let Some(guild_id) = ctx.guild_id() {
-        let new_user = NewUser {
-            discord_id: ctx.author().id.0 as i64,
-            guild_id: guild_id.into(),
-            first_name,
-            last_name,
-            email,
-        };
+        let discord_id = ctx.author().id.0 as i64;
 
         {
             let mut conn = ctx.data().pool.get()?;
-            new_user.insert(&mut conn);
+
+            if User::get(&mut conn, guild_id.into(), discord_id)?.is_some() {
+                ctx.say("You've already been registered.").await?;
+
+                return Ok(());
+            }
+
+            let new_user = NewUser {
+                discord_id,
+                guild_id: guild_id.into(),
+                first_name,
+                last_name,
+                email,
+            };
+
+            new_user.insert(&mut conn)?;
         }
 
         ctx.say("You have been registered.").await?;