Added clippy to CI and fixed all clippy warnings (#613)

* Fixed all clippy warnings.

* Added `clippy` to CI.

* Reverted an unwanted change + Applied `cargo fmt`.

* Fixed the idiom version.

* Revert "Fixed the idiom version."

This reverts commit 6f78be0d42.

* Fixed clippy issues on CI.

* Revert "Fixed clippy issues on CI."

This reverts commit a9fa6ba189.

* Revert "Reverted an unwanted change + Applied `cargo fmt`."

This reverts commit 6bd37b6479.

* Revert "Fixed all clippy warnings."

This reverts commit d1f3b847e3.

* Removed Clippy

* Removed Lint

* `admin.rs` clippy fixes.

* Applied more clippy changes.

* Even more clippy changes.

* `client.rs` clippy fixes.

* `server.rs` clippy fixes.

* Revert "Removed Lint"

This reverts commit cb5042b144.

* Revert "Removed Clippy"

This reverts commit 6dec8bffb1.

* Applied lint.

* Revert "Revert "Fixed clippy issues on CI.""

This reverts commit 49164a733c.

src/pool.rs

@@ -241,20 +241,17 @@ impl ConnectionPool {
                 let old_pool_ref = get_pool(pool_name, &user.username);
                 let identifier = PoolIdentifier::new(pool_name, &user.username);
 
-                match old_pool_ref {
-                    Some(pool) => {
-                        // If the pool hasn't changed, get existing reference and insert it into the new_pools.
-                        // We replace all pools at the end, but if the reference is kept, the pool won't get re-created (bb8).
-                        if pool.config_hash == new_pool_hash_value {
-                            info!(
-                                "[pool: {}][user: {}] has not changed",
-                                pool_name, user.username
-                            );
-                            new_pools.insert(identifier.clone(), pool.clone());
-                            continue;
-                        }
+                if let Some(pool) = old_pool_ref {
+                    // If the pool hasn't changed, get existing reference and insert it into the new_pools.
+                    // We replace all pools at the end, but if the reference is kept, the pool won't get re-created (bb8).
+                    if pool.config_hash == new_pool_hash_value {
+                        info!(
+                            "[pool: {}][user: {}] has not changed",
+                            pool_name, user.username
+                        );
+                        new_pools.insert(identifier.clone(), pool.clone());
+                        continue;
                     }
-                    None => (),
                 }
 
                 info!(
@@ -399,7 +396,7 @@ impl ConnectionPool {
                             },
                         };
 
-                        let reaper_rate = *vec![idle_timeout, server_lifetime, POOL_REAPER_RATE]
+                        let reaper_rate = *[idle_timeout, server_lifetime, POOL_REAPER_RATE]
                             .iter()
                             .min()
                             .unwrap();
@@ -489,7 +486,7 @@ impl ConnectionPool {
                             .clone()
                             .map(|regex| Regex::new(regex.as_str()).unwrap()),
                         regex_search_limit: pool_config.regex_search_limit.unwrap_or(1000),
-                        default_shard: pool_config.default_shard.clone(),
+                        default_shard: pool_config.default_shard,
                         auth_query: pool_config.auth_query.clone(),
                         auth_query_user: pool_config.auth_query_user.clone(),
                         auth_query_password: pool_config.auth_query_password.clone(),
@@ -678,7 +675,7 @@ impl ConnectionPool {
             let mut force_healthcheck = false;
 
             if self.is_banned(address) {
-                if self.try_unban(&address).await {
+                if self.try_unban(address).await {
                     force_healthcheck = true;
                 } else {
                     debug!("Address {:?} is banned", address);
@@ -806,8 +803,8 @@ impl ConnectionPool {
         // Don't leave a bad connection in the pool.
         server.mark_bad();
 
-        self.ban(&address, BanReason::FailedHealthCheck, Some(client_info));
-        return false;
+        self.ban(address, BanReason::FailedHealthCheck, Some(client_info));
+        false
     }
 
     /// Ban an address (i.e. replica). It no longer will serve
@@ -931,10 +928,10 @@ impl ConnectionPool {
         let guard = self.banlist.read();
         for banlist in guard.iter() {
             for (address, (reason, timestamp)) in banlist.iter() {
-                bans.push((address.clone(), (reason.clone(), timestamp.clone())));
+                bans.push((address.clone(), (reason.clone(), *timestamp)));
             }
         }
-        return bans;
+        bans
     }
 
     /// Get the address from the host url
@@ -992,7 +989,7 @@ impl ConnectionPool {
         }
         let busy = provisioned - idle;
         debug!("{:?} has {:?} busy connections", address, busy);
-        return busy;
+        busy
     }
 
     fn valid_shard_id(&self, shard: Option<usize>) -> bool {
@@ -1031,6 +1028,7 @@ pub struct ServerPool {
 }
 
 impl ServerPool {
+    #[allow(clippy::too_many_arguments)]
     pub fn new(
         address: Address,
         user: User,
@@ -1043,7 +1041,7 @@ impl ServerPool {
     ) -> ServerPool {
         ServerPool {
             address,
-            user: user.clone(),
+            user,
             database: database.to_string(),
             client_server_map,
             auth_hash,