Upgrade to Actix V2, bump SQLX version, code cleanup, intergrate ratelimiter (#288)

* Upgrade to Actix V2, bump SQLX version, code cleanup, intergrate ratelimiter

* Add pack file path validation

* Fix compilation error caused by incorrect merge

src/ratelimit/mod.rs

@@ -0,0 +1,64 @@
+use std::future::Future;
+use std::marker::Send;
+use std::pin::Pin;
+use std::time::Duration;
+
+use crate::ratelimit::errors::ARError;
+use actix::dev::*;
+
+pub mod errors;
+pub mod memory;
+/// The code for this module was directly taken from https://github.com/TerminalWitchcraft/actix-ratelimit
+/// with some modifications including upgrading it to Actix 4!
+pub mod middleware;
+
+/// Represents message that can be handled by a `StoreActor`
+pub enum ActorMessage {
+    /// Get the remaining count based on the provided identifier
+    Get(String),
+    /// Set the count of the client identified by `key` to `value` valid for `expiry`
+    Set {
+        key: String,
+        value: usize,
+        expiry: Duration,
+    },
+    /// Change the value of count for the client identified by `key` by `value`
+    Update { key: String, value: usize },
+    /// Get the expiration time for the client.
+    Expire(String),
+    /// Remove the client from the store
+    Remove(String),
+}
+
+impl Message for ActorMessage {
+    type Result = ActorResponse;
+}
+
+/// Wrapper type for `Pin<Box<dyn Future>>` type
+pub type Output<T> = Pin<Box<dyn Future<Output = Result<T, ARError>> + Send>>;
+
+/// Represents data returned in response to `Messages` by a `StoreActor`
+pub enum ActorResponse {
+    /// Returned in response to [Messages::Get](enum.Messages.html)
+    Get(Output<Option<usize>>),
+    /// Returned in response to [Messages::Set](enum.Messages.html)
+    Set(Output<()>),
+    /// Returned in response to [Messages::Update](enum.Messages.html)
+    Update(Output<usize>),
+    /// Returned in response to [Messages::Expire](enum.Messages.html)
+    Expire(Output<Duration>),
+    /// Returned in response to [Messages::Remove](enum.Messages.html)
+    Remove(Output<usize>),
+}
+
+impl<A, M> MessageResponse<A, M> for ActorResponse
+where
+    A: Actor,
+    M: actix::Message<Result = ActorResponse>,
+{
+    fn handle(self, _: &mut A::Context, tx: Option<OneshotSender<Self>>) {
+        if let Some(tx) = tx {
+            let _ = tx.send(self);
+        }
+    }
+}