Add authorize command

Motivation:

The library provides command implementations for almost every single Redis command, authorize is no different.

Modifications:

Add `authorize(with:)` command method on `RedisClient`
Replace the implementation in `RedisConnection.connect(...)`

Result:

Developers should now have independent access to the `AUTH` Redis command on `RedisClient` implementations.

Author: Mordil

Sources/RediStack/Commands/BasicCommands.swift

@@ -71,6 +71,18 @@ extension RedisClient {
             .convertFromRESPValue(to: String.self)
             .map { return $0 == "OK" }
     }
+    
+    /// Requests the client to authenticate with Redis to allow other commands to be executed.
+    ///
+    /// [https://redis.io/commands/auth](https://redis.io/commands/auth)
+    /// - Parameter password: The password to authenticate with.
+    /// - Returns: A `NIO.EventLoopFuture` that resolves if the password was accepted, otherwise it fails.
+    @inlinable
+    public func authorize(with password: String) -> EventLoopFuture<Void> {
+        let args = [RESPValue(bulk: password)]
+        return send(command: "AUTH", with: args)
+            .map { _ in return () }
+    }
 
     /// Removes the specified keys. A key is ignored if it does not exist.
     ///

Sources/RediStack/RedisConnection.swift

@@ -71,10 +71,8 @@ extension RedisConnection {
                 guard let pw = password else {
                     return connection.eventLoop.makeSucceededFuture(connection)
                 }
-                
-                let args = [RESPValue(bulk: pw)]
-                return connection.send(command: "AUTH", with: args)
-                    .map { _ in return connection }
+                return connection.authorize(with: pw)
+                    .map { return connection }
             }
     }
 }